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Supyect No. 3 RECEIVING THE CONTROL DOSE. NOTE THE BANDAGE, THE EXPERI- 
MENTAL PIPE AND THE ELECTRIC WIRE WOUND AROUND THE ARM OF THE EXPERI- 
MENTER TO PREVENT DETECTION BY THE SUBJECT. 


4 
VOL, XXXIII WHOLE NO. 150 
PSYCHOLOGICAL REVIEW PUBLICATIONS 


NO. 3 1924 






“ MAY %% 192 
Psychological Monographs ; 
EDITED BY iG 


JAMES ROWLAND ANGELL, Yate University 
HOWARD C. WARREN, Princeton University (Review) 
JOHN B. WATSON, New York (J. of Exp. Psychol.) 
MADISON BENTLEY, Unrversiry or Itutrnors (Inder) 
S. W. FERNBERGER, Unrversity or Pennsytvania (Bulletin) 


The Influence of Tobacco Smoking 
on Mental and Motor Efficiency 


An Experimental Investigation 


BY 


my 
CLARK L. HULL 


Associate Professor of Psychology 
and Director of the Psychological Laboratory, 
University of Wisconsin 


PSYCHOLOGICAL REVIEW COMPANY 
PRINCETON, NJ. 


Acents: G. E. STECHERT & CO., Lonpon (2 Star Yard, Carey St., W.C.) 
Parts (16 rue de Condé) 


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CONTENTS 


Chapter 

J’ Summary of Previous Investigations .......... 

II The Problem and Methods of Investigation .. 

III The Effect of Smoking on the Heart Rate . 
IV The Effect of Smoking on the Steadiness of the 
RAM IMRR oor ye ee tea teu AY ko eres ew ea 
V_ The Effect of Smoking on the Rate of Voluntary 
USES TECVIS' 5 Air, oll hei Seki la a ly, Reg A ae 
._ VI The Effect of Smoking on Muscular Fatigue ... 
VII The Effect of Smoking on the Rate of Cancelling 
Poe Be aaa ck cae haem Feat eae ie a matte ie 
VIII The Effect of Smoking on the Accuracy of Can- 
COALITIC ae SUP enna Sees Bi sich) Bh @ aA) Wi ate Cts 
IX The Effect of Smoking on the Speed of Oral Read- 
movoialsolatedi Nw Ordsye. tenes en wee ale ayre} 
X The Effect of Smoking on the Speed of Oral Re- 
action to Freshly Learned Material .......... 
XI The Effect of Smoking on the Speed of Contin- 
PMV t AEA OILIOT Gre Wak co ea lacs ol oe yale me's 
XII The Effect of Smoking on the Accuracy of Con- 
VESTS E SIUC Te VOWS (6 V1 Ta 0 Raa Ale i oad mu ge oP 
XIII The Effect of Smoking on the Auditory Memory 
BOAT RCTS LITO Gi tae ee eh mes a Al Si 
XIV The Effect of Smoking on the Rate of Learning 
fever ounuinary and Conclusions 0... eve aa ee 


104 


116 


122 
12 


IAI 


Appendix 

Ac» J. Wa. Payne'’sa hesults tone rear atege tae 
G. A. Dowling’s Results on Heart Rate ....... 
Warren P. Lombard’s Results on Muscular Fatigue 
Vaughan Harley’s Results on Muscular Fatigue .. 
Theodore Hough’s Results on Muscular Fatigue .. 
GS) Berrys esults;on - Adding ica aves ee 
Summary of Froeberg’s Results .... opposite p. 
Baumbercer and ‘Martin sjkestlts 22 \s30 2) tae 


Meylan’s Results on Smoking and Scholarship ... 


ee ac Gili sie ler) Gr eS 


The Results from a Subject who Discovered the 
Control Dose 0202 hae o Tie eet ee ee 


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INTRODUCTORY NOTE 


In 1917 the American Committee for the Study of the Tobacco 
Problem appointed a subcommittee on Educational Aspects, and 
the writer of this note was made chairman of that committee. 
After a year or more of preliminary study, it became apparent to 
him that it would be desirable to broaden the investigation, with a 
view particularly to making tests in the psychological laboratory 
to determine if possible by precise measurements the effect of to- 
bacco upon intellectual process. So the writer proposed to the Amer- 
ican Committee that the problem assigned to him for investigation 
should be entitled, “Tobacco and Mental Efficiency,” and that an 
‘appropriation should be made to defray the expenses of prelimina- 
ry experimentation for the purpose of attempting to develop suit- 
able technique for the laboratory study of the effect of tobacco on 
mental activities. The American Committee accepted these sug- 
gestions and provided adequate funds for an exploration of the 
matter in hand. The writer then laid before Dr. Clark L. Hull, As- 
sociate Professor of Psychology and Director of the psychological 
laboratories in the University of Wisconsin, the problem which 
he wished to have investigated, and asked if he could spend the 
summer of 1919 in developing a technique for the study of the 
relation of tobacco to mental efficiency. Dr. Hull consented to do 
this. The results of the summer’s work showed conclusively to 
Dr. Hull, to the writer and to the American Committee that it 
was possible to measure the effect of tobacco upon the mental 
processes with a high degree of accuracy. The writer then secured 
from the American Committee a generous appropriation of funds 
for the prosecution of the laboratory investigation, which was 
placed in charge of Dr. Hull, who was thus enabled to secure sub- 
jects and trained assistants in order to carry through the investi- 
gation in a thorough-going way. This volume presents the results 
of the investigation, together with a summary of the results of 
previous investigations and a discussion of the methods employed 
to secure reliable data uncomplicated by disturbing factors. 


2 CLARKUL HOLE 


The writer has followed the laboratory investigation through- 
out with genuine interest, and he is convinced that the data secured 
and the conclusions reached are of unusual importance. Dr. Hull 
has succeeded in developing a technique to overcome difficulties in 
the investigation of the drug effects of tobacco which no previous 
investigator, so far as the writer knows, has been able to overcome. 
The report is presented in a concrete, clear, and attractive form, 
so that it may be read with pleasure and profit by any one who is 
interested in psychological investigation and also by those who 
wish to find out for their own information or for the guidance of 
others whether tobacco exerts any measurable influence upon the 
intellectual processes. 

It should be specially noted that this laboratory study constitutes 
but one phase of a broader investigation of the relation between 
tobacco and mental efficiency. Because of the extent and impor- 
tance of the results of the laboratory investigation, it has been 
deemed advisable to publish them separately in this volume. An- 
other volume presenting the results and conclusions of the investi- 
gation as a whole, and showing the connections between the data 
derived from the laboratory and from several other sources will 
be published by the writer, under whose direction the various 
phases of the investigation have been carried on. 


The University of Wisconsin M. V. O’SHEA. 
May, 1922. 


PREFACE 


The circumstances under which the investigation reported in 
the following pages was carried out, require a brief statement. In 
May of 1919, Professor M. V. O’Shea of the Department of 
Education of the University of Wisconsin, stated to the writer 
that the American Committee for the Study of the Tobacco Prob- 
lem of which he was a member, had appointed him chairman of a 
sub-committee which had been created for the purpose of investi- 
gating the effects of tobacco on the intellectual processes. In this 
connection he requested the writer’s opinion as to the feasibility 
of an experimental attack upon the problem. The reply was that 
the success of such an experiment would depend very largely on 
whether or not a neutral control dose could be devised which would 
not be distinguished by the subject from the actual tobacco. As 
the result of this conference the writer undertook to spend the 
following summer in determining the practicability of the project. 

The first six weeks of this period were consumed in devising 
and assembling apparatus and tests, and in perfecting the exceed- 
ingly delicate technique. During this period three subjects were 
experimented on in an extensive series of preliminary tests; the 
numerical results of which were discarded. These preliminary 
experiments having shown beyond a doubt the feasibility of the 
neutral control dose and the adequacy of the technique in general, 
two subjects (1 and 2) of the regular series reported in the fol- 
lowing pages, were put through the experiment. A detailed report 
of the summer’s investigation was then made. 

Upon the basis of this report, together with Professor O’Shea’s 
recommendation, the American Committee for the Study of the 
Tobacco Problem made a generous appropriation for the conti- 
nuation of the investigation, and the writer agreed to see the work 
through to completion. It was understood that the investigation 
together with the final report of the fiindings, were to be strictly 
scientific and impartial, and that the present writer should have 
the right of publication of the results, regardless of whether they 


4 CLARK L. HULL 


should turn out to be favorable or unfavorable to tobacco. It was 
also agreed that an adequate supply of subjects together with a 
number of trained laboratory and statistical assistants should be 
provided at the expense of the committee. 

The assistants, in addition to a previous thorough training in 
experimental psychology, were each given special training and 
instruction in his duties before entering upon them. The writer-is 
glad to take this opportunity of expressing his deep debt of grati- 
tude for the splendid, unselfish service of these people. Without 
their loyal assistance and cooperation, the enormous labor involved 
in this investigation could not possibly have been performed. The 
feeble recognition of their work possible in this place is very in- 
adequate compensation for their weeks, and in some cases months, 
of most exacting service. Arranged chronologically, their names 
are: 


FRED G. MUELLER 

Bertua lutzi HuLt (Statistician) 
CouRTNEY SHERMAN 

E. A. CULLER 

CHESTER H. MATRAVERS 

Fitip ForsBpecK 

EVERETT F, PATTEN 


The work of each deserves special mention. 


Mr. Mueller conducted the tests on six subjects, a total of over 
100 evenings of continuous experimentation. Mr. Mueller also 
contributed a number of valuable suggestions regarding the tech- 
nique of the experiment. 

Mrs. Hull scored the great mass of test results atid made the 
primary computations, for the greater part of the subjects em- 
ployed in the investigation. 

Mr. Sherman and Mr. Culler each carried one subject through 
the tests, Mr. Sherman having himself previously served as a 
subject. 

Mr. Matravers carried three subjects through the experiment 
and did the scoring and primary statistical work on two, after 
having himself served as a subject. 


THE INFLUENCE OF TOBACCO SMOKING 5 


Mr. Patten gave the tests to three subjects, besides scoring the 
test results and making the primary computations on four subjects. 

The writer wishes to thank the American Committee for the 
Study of the Tobacco Problem for the most generous grant 
of funds which alone made the present work possible. In parti- 
cular, he is under obligation to Professor M. V. O’Shea who, 
throughout the protracted investigation, has been a source of 
encouragement and inspiration. 

Lastly, thanks are due Dr. W. W. Garner, Director of Tobacco 
Investigations, U. S. Department of Agriculture, who very kindly 
made a careful chemical analysis of the tobacco used in the present 
investigation. 


Madison, Wisconsin. CiarkK L. Huy 
July, 1922. 


THE INFLUENCE OF TOBACCO SMOKING ON 
MENTAL AND MOTOR EFFICIENCY 


CHAP Dikal 


SUMMARY OF PREVIOUS INVESTIGATIONS 


In so far as they relate to the present study, previous investiga- 
tions of the effects of smoking may be divided into three general 
groups: a physiological group, a psychological group, and a sta- 
tistical group. In the interests of clearness of presentation in the 
following pages, each group will be considered separately. 

The studies of the physiological group are all experimental in 
nature. They report the effects of tobacco on such processes as 
heart rate, blood pressure, steadiness, precision of voluntary 
movement, and muscular fatigue. 

Several of the writers who have experimented on the influence 
of tobacco have observed more or less casually that the heart rate 
was increased after smoking. The problem was investigated sys- 
tematically in 1914 by J. W. Payne.* He used ten subjects of whom 
six were habitual smokers. These subjects were tested on the aver- 
age between four and five days each, just before and immediately 
after smoking a cigar, with an approximately equal number of 
control days. Several of the subjects smoked cigarettes on ad- 
ditional days. Payne reports a marked tendency to increase of 
both heart rate and blood pressure, but does not give averages. 
The present writer has computed from Payne’s published data the 
average net increase of the pulse rate on the tobacco days (Ap- 
pendix A). It amounts to an increase of 7.98 beats per minute for 
the horizontal position and 6.94 beats for the vertical or standing 
position. The cigarette results, while not strictly comparable be- 
cause incomplete, suggest a stimulation about half as great. Com- 
putation of the statistical reliability of the above averages indi- 


1 Fisher and Berry, The Physical Effects of Smoking, pp. 1-43. 


THE INFLUENCE OF TOBACCO SMOKING 7 


cates that there is only one chance in several thousand but that. 
there is a net stimulation on the tobacco days. 

Two years later Dowling’ attempted to determine experimental- 
ly the influence of smoking two cigars on the return of the heart 
rate to normal after exercise. Unfortunately his experiment was 
set up in such a manner that it could not reveal any disturbance in 
this function even if present. In addition, his methods of computa- 
tion are so faulty that his statements of results are also misleading. 
Fortunately he publishes his original data. A somewhat laborious 
computation from these data for his habitual-smoker subjects 
shows (Appendix B) that strenuous jumping after smoking leaves 
the heart rate between six and seven beats per minute faster, on 
the average, than similar exercise without smoking. But since, ac- 
cording to Payne’s results, we should expect approximately this 
amount of stimulation from the tobacco alone and regardless of 
exercise, Dowling’s conclusion that tobacco causes the increase in 
heart rate resulting from exercise to persist longer than normal, 
is without support. Dowling also claims that the normal pulse of 
smokers is higher than that of non-smokers. A computation of the 
reliability of the difference found between the average pulse of his 
smokers and non-smokers shows, however, that the difference 
found is no more than ordinary chance might produce. 

As to precision of voluntary movement, there is abundant evi- 
dence that tobacco smoking markedly reduces it. This matter was 
investigated experimentally by Blickley in 1915,° with 14 subjects. 
He found that after smoking two cigars there was a marked di- 
minution in precision of tracing a line with a fountain pen be- 
tween two other lines arranged in a zig-zag course and about two 
millimeters apart. He found a somewhat smaller loss with the 
same subjects in lunging at a target with a foil. Unfortunately 
Blickley’s non-smoking days were so complicated by irrelevant 
exercise of a strenuous nature that his control results are not re- 
liable. Consequently the exact percentages of loss reported by him 
are not significant, though it is quite evident that the smoking 
caused a certain amount of loss in efficiency. The following year 


2 Fisher and Berry, op. cit., pp. 43-79. 
8 Fisher and Berry, op. cit., pp. 79-125. 


8 CLARK LABULE 


Lang* continued the investigation, using eight subjects. The ac- 
tivity chosen was throwing base balls at a target. In this case the 
control days appear to be reliable though as usual no control dose 
was used. Lang’s subjects show an average net loss in efficiency 
of 21.5% after smoking one cigar and of 24% after smoking two. 
In 1919, Oscar J. Johnson in connection with a psychological 
investigation,’ reported two experiments which bear on our pre- 
sent problem. The results of his first experiment are not significant. 
In his second experiment he tested the influence of smoking a cigar 
upon accuracy of aiming and steadiness of motor control. The 
aiming appears to have been done with a stylus at a small hole. 
Steadiness was measured by holding a stylus within a small hole 
so as to touch the edge as rarely as possible. He used four subjects 
who served from one to four days each. Their habits as to smok- 
ing are not stated. No control records of any kind were taken. The 
experiment is consequently inadequate, not only as to control but 
also as to the number of subjects and particularly the number of 
tests made on each. He reports after smoking an average increase 
of contacts (loss of efficiency) in the aiming test of 342% and in 
the steadiness test, of 192%. While probably no special signifi- 
cance should be attached to the size of the above percentages for 
reasons pointed out above, it is significant that they agree with 
the results already examined as to the nature of the effect pro- 
duced. Johnson also reports a slight loss in the speed of tapping. 
The following year (1920) Froeberg® published as a part of an 
experiment mainly psychological in nature, some results as to the 
influence of smoking a cigar on precision of voluntary movement 
(coordination), steadiness, and rate of tapping. In this case mus- 
cular precision was measured by the distance a stylus could be 
drawn down a narrow V-shaped slit without touching the side. 
Froeberg used five non-smokers as subjects and tested them im- 
mediately after smoking on eight days. They were also tested on 
eight control days. This experiment is especially interesting be- 
cause it contains the first and only attempt recorded in the litera- 


4 Fisher and Berry, op. cit., pp. 126-172. 
5 Psychological Clinic, Vol. 12, pp. 132 ff. and 230 ff. 
6 Journal of Experimental Psychology, Vol. 3, p. 334 ff. 


THE INFLUENCE OF TOBACCO SMOKING 9 


ture to provide a control dose in tobacco-smoking experimentation. 
On the control days the subjects smoked just as on the other days 
except that the smoke first passed through cotton wool before 
reaching the mouth of the smoker. This was done on the theory 
that the passage of the smoke through the cotton would remove 
from it all of its physiologically active constituents, though this 
may be open to question. The method was abandoned, however, 
after the third subject, the remaining subjects smoking nothing on 
the control days. The results from this squad of subjects are there- 
fore a little uncertain in meaning because of the mixed and some- 
what questionable nature of the control results. Under these condi- 
tions, Froeberg found that muscular precision lost 23.5% in ef- 
ficiency and steadiness lost over 120%. His results in tapping show 
a slight increase in efficiency on the tobacco days, though it is too 
small to be significant. 

We find, then, despite certain defects of procedure in some of 
the experiments, a consistent agreement among the various in- 
vestigators that the immediate effect of tobacco smoking is to 
diminish very markedly the precision of voluntary movement. 
This at least may be regarded as established. With this loss of 
muscular precision probably goes also an increase in muscular tre- 
mor. The results as to rate of tapping are inconclusive. 

The first and best study concerning the effect of tobacco on 
muscular fatigue was reported by Lombard in 1892.’ The study 
in question was an extensive investigation of the influence of such 
factors as hunger, sleep, temperature, barometric pressure, and 
alcohol. Among other things, he investigated the influence of 
smoking cigars. The criterion used was the amount of work per- 
formed by his middle finger on the weight ergograph. The part of 
his experiment concerned with tobacco occupied eleven days, four 
of which were control days. Usually five tests were made each day. 
On the tobacco days he smoked a cigar just before each test, on the 
control days he did nothing. The control days average 16.027 
kilogrammeters of work whereas the drug days average only 


7 Lombard, Warren P. Some of the Influences which Affect the Power of 
Voluntary Muscular Contraction. Journal of Physiology, 1892, Vol. 13, pp. 1-58. 
The results of this investigation of the effects on tobacco are found on pp. 44-48. 


room CLARK L. HULL 


11.375, which is a decrease of over 29%. The present writer has 
computed the statistical reliability of this difference (Appendix 
C), and it appears that it could only happen by pure chance in about 
one case in a hundred. This is considered a very satisfactory re- 
liability. Unfortunately it is impossible to say with any confidence 
whether this difference reflects merely a personal peculiarity in 
Lombard’s reaction to the drug, or even whether it was caused -by 
the tobacco at all, since no control dose was used. 

Two years later in connection with an extensive investigation 
of the influence of sugar upon work done with the weight ergo- 
graph, Harley considered briefly the influence of cigar smoking.* 
He tested the middle finger of each of his hands a variable number 
of times each day for five days. Two of these were control days. 
His results, while suggesting a slight loss in efficiency on the to- 
bacco days, are so variable and so small in number that they are 
practically without value. The statistical reliability has been com- 
puted for Harley’s results, both as to amount of work done and 
as to the length of time before exhaustion (Appendix D). The 
difference found in the former might have happened by chance 
in about one case in five, the latter in about two cases in five. 
Neither is significant. 

In 1901, Hough reported a brief experiment on the effect of 
smoking upon muscular efficiency.® As in the two previous studies, 
this also was incidental to a much larger investigation. Unfor- 
tunately he used a spring ergograph which yields a markedly differ- 
ent work or fatigue tracing from that given by the weight ergo- 
graph used by the other investigators in this field. Hough pub- 
lishes the results of only two regular smoking days. From his pub- 
lished tables, the results of four other days were found which may 
evidently be used as controls. Hough concludes that the tobacco 
had no influence whatever upon the amount of work performed by 
him, but that it did have a marked influence in delaying the onset 
of fatigue. This was shown in his results by the slower fall of the 
work curve to the “fatigue level.” Computation shows (Appendix 


8 Harley, Vaughan. The Value of Sugar and the Effect of Smoking on 


Muscular Work. Journal of Physiology, 1894, Vol. 16, pp. 97-122. 
® Hough, Theodore. American Journal of Physiology, 1901, Vol. 5, pp. 240- 


266. . 


THE INFLUENCE OF TOBACCO SMOKING II 


E) that there is only about one chance in thirty-three of his ob- 
taining such a difference without some cause for it. But as with 
Lombard’s results we are unable to say whether this was due to 
the tobacco at all, since no control dose was used. His technique, 
while otherwise excellent, is so different from Lombard’s that a 
strict comparison of the two findings is impossible. 

The last study on tobacco and fatigue was reported by Rivers 
in 1908 in connection with an extensive investigation chiefly of 
the influence of alcohol and caffeine.*® He used two subjects. One 
had two drug days with three control days and the other had two 
drug days and two control days. Rivers does not give numerical 
results but states that the drug days were, upon the whole, slightly 
less efficient than the control days but no more so than might re- 
sult from chance. 

The evidence as to the influence of tobacco smoking upon mus- 
cular fatigue, while suggesting a slight loss in efficiency, is thus seen 
to be conflicting and generally unsatisfactory. The studies have all 
been incidental to other investigations and have been based upon 
an entirely inadequate number of subjects usually working on an 
entirely inadequate number of days. Moreover, no control dose 
was used in any of them which makes the results subject to various 
constant errors of unknown proportions, such as suggestion and 
the excitement of interest. Even Rivers who has done such excel- 
lent service in pointing out the dangers from just such sources in 
all kinds of drug experimentation, used no control dose in his 
tobacco experiments. We must therefore reserve decision in this 
important matter until more adequate experimental evidence is 
available. 

The first significant experiment as to the influence of tobacco on 
the mental processes was reported by Bush in 1914." He used fif- 
teen subjects, all but two of whom were habitual smokers. These 
men were each tested five times immediately after fifteen minutes 
of quiet smoking and five times when reasonably free from the 
effects of smoking. Unfortunately no regular control tests seem 


10 Rivers, W. H. R. The Influence of Alcohol and Other Drugs on Fatigue, 


1908, pp. II12-I14. 
11 New York Medical Journal, Vol. 94, pp. 519-527. 


12 CLARK LEAHO EL 


to have been made on the subject themselves, as was done in so 
many of the experiments considered above. One subject not of the 
regular smoking squad was put through the tests as a control sub- 
ject, however, and the results of the other fifteen were corrected 
according to his performance. Under these conditions, Bush re- 
ports that his subjects as a group show a loss in efficiency on every 
one of the ten mental tests used, the average loss of the ten tests 
being about 10%. The various tests together with the average loss 
on each, follow: Cancellation (A-test and E-test), —17%; free 
(chain ) association, —9% ; free association (to nonsense syllables ) 
—8 % ; free association (to nouns and verbs), —22% ; controlled 
association (opposites) test, —14% ; controlled association (ge- 
nus-species) test, —12%j; addition, —9%; subtraction, —7%; 
memory span (visual presentation), —3% ; memory span (audi- 
tory presentation, —9%. 

In discussing the reliability of Bush’s experiment, Froeberg re- 
marks :* “In spite of the apparent care with which this investiga- 
tion was made, there are in it certain defects sufficient to cast 
serious doubts upon the validity of the results. In the first place 
the results from the smokers were ‘corrected’ by those from a nor- 
mal ‘control.’ But the results from only one subject averaged as 
they were from only five experiments, can scarcely be considered 
sufficiently ‘normal’ to be used as a standard for the other fifteen.” 
Even had a number of control subjects been used instead of one, 
the control would have been inadequate. One man can never safely 
be used as a control for another, since the various factors requiring 
control are sure to differ more or less from man to man. For this 
reason the only proper control subject for a man is the man himself. 
To make matters worse, no control dose was used, which throws 
the results open to all the pernicious influences of interest, excite- 
ment, prejudices, and suggestion. In this connection it is interest- 
ing to note that Bush actually threw out the results of certain of 
his subjects because of their failure to apply themselves “impar- 
tially.”’ This is unfortunate, but under such experimental condi- 
tions it is difficult to see how an experimenter should be certain that 
any of his subjects were applying themselves impartially. 


12 Froeberg, op. cit., p. 336. 


THE INFLUENCE OF TOBACCO SMOKING 13 


The next psychological study on the effects of smoking was re- 
ported by Charles Scott Berry in 1917.° He was his own subject 
and an habitual smoker. For ten evenings immediately after din- 
ner he smoked a cigar and then tested himself on rate and ac- 
curacy of addition. On alternate (control) evenings he spent the 
corresponding time in conversation or light reading and then added 
as on the drug evenings. The test was to do fifteen examples in 
addition, each consisting of ten columns of ten digits each. Berry 
reports an average advantage for the smoking evenings of 7.7% 
in speed of addition and an advantage of 4.5% in accuracy. Berry’s 
results are somewhat complicated by practice effects so that they 
cannot be taken quite at their face value. After correction has been 
made for practice (Appendix I) there appears to be no difference 
whatever in accuracy but a remarkably consistent advantage in 
speed, averaging 6.3% in favor of the tobacco evenings. Compu- 
tation of the statistical reliability of this difference shows that it 
could only have come about by chance in one case in several 
thousand and is therefore extremely reliable. Unfortunately these 
results represent the reaction of but one subject and no control 
dose was used even with him. There is the additional possibility 
that the advantage found on the tobacco evenings was really due 
to privation or withdrawal effects which might have caused ab- 
normally small scores on the control evenings. 

Johnson’s experiment (1918) has already been mentioned in 
connection with the effect of tobacco on the precision of move- 
‘ment. In his second experiment he includes two mental tests: a 
color naming test and an adding test. In the former the score was 
the time required to name one hundred colors, in the latter the 
time required to add the figure seven to one hundred two-place 
numbers. He reports a loss in efficiency in color naming of 11.5% 
immediately after smoking and one of 5.3% two hours later. Re- 
garding the effect on adding, he says: “Here we have rather un- 
expected results, in that the time to add is shortened considerably 
in most instances’ (1.e., after smoking).** Johnson’s various 
tabular statements as to the effects on adding, while possibly not 


18 Psychological Bulletin, 1917, Vol. 14, pp. 25-28. 
14 Op. cit., p. 231. 


14 CLARKVLY HULL 


entirely consistent, seem to show a slight immediate loss followed 
by a considerable gain. It is not stated whether the subjects were 
habitual smokers or not. For reasons pointed out on page 8 the 
results of this experiment are of uncertain value. 

Reference has already been made to Froeberg’s work. He re- 
ports two experiments, the first of which was described above 
(p. 8). The results of the psychological part of this experiment 
are for the most part discordant and indecisive, though the ten- 
dency inclines to a loss in efficiency on the tobacco days. Possibly 
this lack of agreement among the various subjects may be due in 
part to the mixed nature of the control and to the fact that no 
normal tests were given before the dose. The second experiment, 
however, was well planned. Five subjects were used, each being 
tested on six days immediately before and after a half hour of 
smoking. On six alternate days the tests were given as usual only 
the subjects spent the half hour in conversation or light read- 
ing. Five psychological tests were used. As might be expected, the 
results of this experiment are much more consistent, though Froe- 
berg modestly disclaims any statistical reliability for them. The 
present writer has computed the average percentage effect and the 
statistical reliability of the averages of the group of subjects for 
each test (Appendix G). Each of the five tests show an average 
loss in efficiency after smoking and the statistical reliability of 
these averages is fairly satisfactory in most cases, in some ex- 
tremely so. Froeberg’s final results are as follows: Memory span 
for letters, —13.6% ; uncontrolled association test, —13.1% ; op- 
posites test, —4.2% ; adding, —5.9%. In the completion test of 
the Trabue type, no percentage effect could be computed from the 
published data but all subjects show a loss and the reliability of 
the average is high. 

Baumberger and Martin’® report an investigation (1920) of 
the relative output of light and heavy smokers in a large telegraph 
office. The work was chiefly sending and receiving Morse code 
messages. There were seven heavy smokers and five light smokers. 
Tables are given which show the relative output of the two 
groups for each hour of the day and for the day as a whole. 


15 Journal of Industrial Hygiene, 1920, Vol. 2, pp. 207-214. 


ee * 


THE INFLUENCE OF TOBACCO SMOKING 15 


Through incorrect methods of computation, Baumberger and 
Martin conclude that six of these differences are significant. 
A recomputation of the reliability of these differences (Appendix 
H) shows that only one hour of the day has a difference three 
times its probable error. This is the first hour and is in favor of 
the heavy smokers. The sixth hour has a fair reliability, however, 
and is in favor of the light smokers. The difference between the 
two groups for the day as a whole has no significance whatever. 
The weak statistical reliability of the above results is due mainly 
to the small number of subjects. As the writers themselves point 
out, such a study could hardly be conclusive evidence of a causal 
relation between tobacco and efficiency in any case, because of the 
possibility that heavy smokers in general may be originally some- 
what differently constituted as a class from light smokers because 
of the influence of selection. 

The psychological investigations as to the effects of smoking 
on the mehtal processes thus appear for one reason or another to 
be of such a nature that it is extremely risky to draw any general 
conclusions from them. Froeberg’s results, easily the best of the 
series, probably furnish some ground for a belief that smoking 
has a detrimental immediate effect on the mental processes of non- 
smokers. Possibly Berry’s meagre results suggest a stimulating 
effect on habitual smokers. But we have no guarantee that in any 
of these experiments the influence of interest, excitement, prejudice 
and suggestion have been eliminated. Until this is done, the issue 
must remain in doubt. And these things will never be safely elimi- 
nated until there is used a control dose such that the subjects do 
not know when they have smoked and they have not, just as the 
subjects of Rivers and of Hollingworth did not know when they 
had taken caffeine and when they had not. 

The investigations considered above have been directed almost 
entirely to the determination of the immediate effects of smoking. 
Fairly distinct from this is the problem of the effect on general 
mental efficiency of long-continued smoking. Obviously this latter 
problem does not lend itself readily to experimental investigation 
because of the relatively great length of time over which the drug 
must act. We accordingly find investigators resorting to statistical 


16 CLARK AAHGLE 


analysis usually of accidentally available data bearing on the gen- 
eral mental efficiency of habitual smokers and comparing these 
with similar data from non-smokers. The chief interest in these 
investigations has been the influence of smoking on scholarship in 
the secondary schools. Accordingly school marks have generally 
been used as the criterion. A very large number of such studies 
have been reported.** These show with great uniformity that non- 
smokers receive, on the average, better school marks than smokers. 
This may be regarded as established. Of these investigations, four 
stand out from the rest and deserve special mention: that of Seaver 
(1897) ;** that of Clark (1900) ;** that of Meylan (1910) ;*° and 
that of Pack (1912).”° Since Meylan’s investigation was reported 
with more care and insight than the others and illustrates both the - 
weaknesses and possibilities of this method of approach, it alone 
will be examined. 

Dr. Meylan investigated 115 smokers and 108 non-smokers in 
Columbia University. He found some slight physical differences 
between the two groups but much less than were reported by 
Seaver. Extending his investigation to university marks, however, 
he found a very striking difference. Over a period of two years 
the average mark of the non-smokers was 69% while that of the 
smokers was 62%. The same tendency was shown by the fact that 
there were only 4% of failures among the non-smokers as against 
10% among the smokers. It became evident, however, that other 
factors besides smoking were probably contributing to produce 
these differences. Investigation showed, for example, that the 66 
fraternity men involved in the investigation averaged only 59.1% 
as against 68.9 for the non-fraternity men, while the non-fraterni- 
ty men made up the great bulk of the non-smokers. This raised the 
question as to whether fraternity life might not be the causal or at 
least selective factor, rather than tobacco? It was also. found that 
the athletes of the group averaged only 63.2% while the non- 
athletes averaged 68.3%, and that the athletes were much more 

16 Bruce Fink, Tobacco, 1915. The Abington Press, New York. 

17 The Arena, 1897, Vol. 17, pp. 470-477. 

18 The Clark College Record, 1900, pp. 91-08. 


19 Popular Science Monthly, 1910, Vol. 77, pp. 170-177. 
20 Popular Science Monthly, 1912, Vol. 81, pp. 336-344. 


THE INFLUENCE OF TOBACCO SMOKING 17 


apt to be both smokers and fraternity men. This raised the ques- 
tion as to how much of the difference found between the smokers 
and the non-smokers was in reality due to engrossment in ath- 
letics on the part of the smokers? After tabulating these complex 
data in various ways, Meylan finally concluded that while bad 
scholarship is distinctly associated with smoking, it is also distinct- 
ly associated with athletics and fraternities and that it is impos- 
sible to tell how much, if any, of the bad scholarship associated 
with tobacco was really caused by it. The effect of smoking on 
scholarhip is thus left undetermined though Meylan deserves 
much credit for clearly recognizing the extremely complex nature 
and uncertain meaning of such data. 

Had he been acquainted with modern methods of statistical 
analysis, Meylan need not have left his problem in quite such an 
unsatisfactory state. As a matter of fact there are well recognized 
methods which have been derived by mathematicians for the treat- 
ment of just such data. Unfortunately they seem not to have been 
utilized in a single one of the many studies of this kind that abound 
in the literature. The result is that the problem of the effect of 
smoking on scholarship is little if any more nearly solved today 
than it was thirty years ago. In the case of Meylan’s investigation, 
the necessary computations may still be made from his published 
data. These computations have been performed by the present 
writer and appear in Appendix I. It will be recalled that the differ- 
ence in average mark between smokers and non-smokers is 7 points. 
The computations in question show that when the influence of 
athletics is removed this difference suffers a slight reduction. 
When, in addition, the influence of fraternities is removed, it 
shrinks to only 3.4 points or less than half its original size. Mey- 
lan’s data, unfortunately, do not permit us to see what would have 
resulted from still further elimination of complicating factors. It 
should be noted, however, that the above results, while interesting 
as an illustration of method, have no special significance as to the 
actual effect of smoking on scholarship. The probable error is very 
large with such a small number of subjects and especially by the 
only method of computation available. For such results to have 
any considerable reliability there should be 1600 or 2000 subjects. 


18 CLARK. L. HULL 


Moreover, since the inductive method by which the causal relation 
is sought to be proven involves the principles of residues, certainty 
can only be established when all other possible factors influencing 
grades have been eliminated in the manner that athletics and fra- 
ternities were above. One thinks at once of such obvious factors 
as shows, pool halls, gambling, drinking, and especially original 
differences in native intellectual endowment and temperament, In 
all investigations of this kind therefore, errors due to native in- 
dividual differences between smokers and non-smokers should be 
eliminated by securing the school marks of each subject before he 
began to smoke as well as after. 

It should also be emphasized that in all investigations of this 
character involving a considerable questionnaire element with its. 
characteristic dangers of miscarriage, a carefully planned control 
should be carried out. The material for such a control may be 
secured by including in the questionnaire, provision for securing 
data on one or two variables involving correlations already well 
known. The reliability of the tobacco data obtained by the ques- 
tionnaire may then be judged to a considerable extent by whether 
or not it yields accurate results on these control variables of known 
correlation. We might, for example, record along with the facts 
of primary interest, whether each subject’s eyes were light or 
dark and the same with respect to his hair. If, then, the final com- 
putations should show no higher correlation between deteriora- 
tion of scholarship and smoking than between the former and the 
accidental factor of eye or hair color, say, we may presumably 
regard the tobacco correlation as negligible. On the other hand 
color of eyes and of hair should show a high correlation between 
themselves. If the questionnaire results fail to yield such a correla- 
tion, we must assume something seriously wrong with the data 
and the results of the entire questionnaire immediately fall under 
suspicion. In short, data which either yields a correlation where 
there is known to be little or none, or which fail to yield a correla- 
tion where one is known to exist, cannot be trusted as a guide to 
action. 





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CHAPTER It 
THE PROBLEM AND METHODS OF INVESTIGATION 


The experience of Hollingworth and others has shown that a 
comprehensive investigation of the effects of a drug on the mental 
processes is hardly within the power of a single individual. In the 
present case, even with a number of trained laboratory and sta- 
tistical assistants, it was found impossible to investigate many 
ramifications of the subject. The problem finally settled upon was: 
to determine quantitatively the effect upon the effuency of a dogen 
typical mental and neuro-muscular functions of young men, of 
smoking a large pipe of mild tobacco for a period of 25 minutes, 
the smoking to take place 1% hours after a meal, the smoke to be 
blown from the mouth at once and not inhaled, and the effects to 
be traced fora maximum of 1 hour and 45 minutes after the smok- 
ing ceased. The problem naturally divides itself into four main 
parts: 

1. The effect on non-smokers who have a gastric tolerance 
for the drug... 

2.. The effect upon habitual smokers. 

3. The relative rate of recovery of the various mental and 
motor functions from the effects of smoking. ; 

4. The degree to which habituation establishes a tolerance for 
tobacco with respect to the various forms of behavior investigated. 

The experimental work was performed in the psychological 
laboratory of the University of Wisconsin. A room 12x18 feet in 
size was set apart as a special smoking laboratory and fitted up with 
all the necessary apparatus (Plate 1). the lighting was arranged 
with care so as to give the subject good illumination yet avoid 
glare. Special effort was made to eliminate all distraction of the 
subject’s attention by noise. This was accomplished with the most 
of the subjects by carrying on the experiment during the evening 
when the psychological laboratory was deserted. Three of the sub- 
jects worked afternoons, but during the summer when the general 
laboratory was not in use. 


20 CLARK’ L.-HULLE 


Nineteen subjects were used in the investigation.* Males were 
chosen rather than females because the greater part of the smoking 
of the world is done by men.’ Young adults were chosen because 
they make more reliable subjects than boys or older men. They 
were also more easily secured. The relatively narrow range in the 
ages of the subjects, in conformity with the principle of uniformity 
of experimental conditions, was intended to promote consistency 
of results and ease of interpretation. As to previous smoking hab- 
its, two distinct groups of subjects were used.* The first group 
was composed of nine men who were either occasional smokers or 
abstainers, but who possessed a tolerance for tobacco in the sense 
that smoking ordinarily did not nauseate them. The second group 
of subjects were composed of nine habitual and rather heavy 
smokers. All but two of these were pipe smokers. One other 
smoker subject was employed but his results could not be used for 
reasons given on p. 31. A summary of important personal data for 
the various subjects is given in Table I. 

The program with each subject was experimentation for 3 hours 
per day for 18 consecutive days, regardless of Sundays or holidays. 
It was felt that eighteen days ought to yield a fairly reliable sam- 
ple of a given man’s behavior. It would have been extremely dif- 
ficult, on the other hand, to secure subjects for a much longer 
period under such exacting conditions as were imposed. Four of 
the subjects for one reason or another, were unable to complete 
the entire 18 days as it was. The experiment with each subject was 
run without interruption through this rather long period with the 
purpose of reducing as much as possible the variability of behavior 
from one day to another. It has been the experience of experimen- 


1 Besides the nineteen subjects mentioned, three other subjects were run in an 
extensive preliminary series of experiments, during which the technique was 
perfected. These results were thrown out. 

2 Plans were made at one time to run a squad of young women subjects but 
they had to be abandoned because of lack of time and funds. 

3 The importance of considering the previous smoking habits of subjects has 
not always been sufficiently realized. It seems possible that some of the apparent 
conflicts between the results obtained by different experimenters in this field may 
be attributed to disregard of this important factor. 


THE INFLUENCE OF TOBACCO SMOKING ai 


talists that variability of reactions are less on consecutive days 
than where work is intermittent.* 

The tobacco employed in the experiment was one of the most 
widely used brands for pipe smoking and was uniform through- 
out. It is manufactured in North Carolina and is apparently a 
domestic tobacco of southern growth. It does not ordinarily bite 
the tongue and is regarded by smokers as a mild tobacco. The 
exact chemical constitution of the tobacco used is shown in the 
following table, for which the writer is indebted to Dr. W. W. 
Garner, Director of Tobacco Investigations of the U.S. Depart- 
ment of Agriculture, who made the analysis at the conclusion of 
the investigation: 


(134 oz. sealed tin. Factory No. 256, Dist. of N.C.) 


Moisture 9.51% 
Nicotine 1.60% 
Crude Ash 15.64% 
Water Soluble Ash 5.73% 
Water Insoluble Ash 9.91 %o 


Alkalinity of Ash (Basis of one gram of tobacco 
in terms of c.c. N/Io acid) : 


Soluble Alkalinity Sad Cc. 
Insoluble Alkalinity Le AAC. 
Sugar (calculated as invert sugar) : 
Reducing Sugars 6.62% 
Total Sugars, after inversion 13.63 % 
Increase in reducing sugars by acid 
hydrolosis, calculated as sucrose 6.66 % 


Dr. Garner adds the following comment upon his examination 
of the tobacco: ‘With reference to ash content, the total crude 
ash comes within the limits to be expected of tobacco of the types 
probably forming the larger portion of this product; namely, 
White Burley and bright flue-cured. The purpose of distinguishing 
between soluble and insoluble ash and the alkalinity of the two 
portions is to arrive at an approximation of relative proportion of 
lime and potash salts arid the content of organic acids of the origi- 


4Walter R. Miles, Effect of Alcohol on Psycho-Physiological Functions, 
p. 30, note. 


22 CLARK EEL LE 


nal product. The alkalinity of the ash affords a rough measure 
of organic acids present in the original product. The data obtained 
are within the range to be expected from a mixture of this charac- 
ter. With reference to the sugar content, the flue-cured type nor- 
mally contains rather high percentages, say, 10 to I5 per cent, 
while Burley ordinarily contains much less sugar. The figures ob- 
tained might well be expected and do not seem necessarily. to 
indicate any considerable addition of sugar in the process of manu- 
facture.”’ 

The dose was 25 minutes of smoking, three full puffs in immedi- 
ate succession being taken every 20 seconds. The smoke was im- 
mediately blown from the mouth and never inhaled. Care was also 
taken not to swallow any of the saliva while smoking or for some 
time after. The tobacco actually consumed amounted to approxi- 
mately 5 grams, moist weight as taken from the tin. The pipe used 
was a rather large one. The bowl was 2 centimeters.in diameter at the 
top (inside measurement) 3.9 centimeters deep, and had a capacity 
of 9.2 cubic centimeters when somewhat caked. The tobacco was 
packed down rather firmly into the bowl and almost invariably 
lasted through the 25-minute smoking period without refilling. 
Usually there was left a small quantity of unsmoked tobacco in 
the bottom of the bowl at the end of the period. The stem of the 
pipe was of ordinary hard rubber with a hole 3.4 millimeters in 
diameter. 

In modern drug experimentation, inseparably connected with 
the dose is the troublesome yet insistent matter of the control dose. 
Rivers’ classical statement of this problem is so apt that we may 
follow Hollingworth in quoting it. 

“T can now pass to a feature of method. . . . designed to elim- 
inate the influence of certain psychical factors which have un- 
doubtedly been allowed to affect the results of nearly all who have 
experimented on the action of drugs. Many of these workers have 
considered the possibility that their results may have been in- 
fluenced by suggestion, or of bias towards results which were to 
be expected theoretically, and some have shown that effects similar 
to those following the administration of a drug may be the conse- 
quence of the administration of a wholly inactive substance which 


TABLE | 


Personal data concerning the subjects used in the experiment 
























































Subject] No .of | Group Age | Status Previous smoking habits 
No. Days | 
| Non- | 
1 | 12 aan 25 |Graduate One or two cigarettes per month 
Student 
Junior 
2 12 3 | 22 |Letters Total abstainer 
& Science 
Graduate é 
“ Smoked cigarettes occasionally while in 
ae | | 30 |Student the army, rarely since. 
Junior 
~ 18 : | 22 |Letters One cigar per week 
& Science 
| Senior : 
‘ Smoked regularly from age 10 to 17. 
5 18 : 27 |Letters Hasn’t smoked at all during last three 
| |& Science | years. 
Senior 
6 18 1 26 ies Total abstainer 
& Science 
Junior 
7 18 | _ 27 |Letters Total abstainer 
re ere ira he yy Me Sclence “fossa pede 4 
8 18 | “ 19 eee Smoked cigarettes a little when about 14 
2 ears old, nothing s : 
y Id th ince 
Sener eye aw may Se Sciences! |) i enue 
[ Sophomore ke iets 
sh) Smoked about 20 cigarettes in his life, 
: ag 22 te none within the last five years. 
3 ourse 
een ere) Peters) | ee crn | POOLS ei a Gye Eg New ON 
Graduate Began smoking at about 17. At present 
10 18 |Smoker| 33 |Student smokes about - cigars per day and a 
pipe occasionally. 
| Music Was in the habit of alternating between 
c i d cigarettes, smoking each ex- 
= a 28 Student Lore foe a week or two. Smoked 
four or five times per day. Inhales. 
Junior : 
ss c tes per day 
12 18 23 +|Letters Smokes numerous cigaret 
fs and also a pipe. 
| & Science 
| Seni ; 
13 18 is 24 ss mn Smokes pipe after each meal and even- 
A ings while studying. 
ee ei |e Agnertare |S eee 
| Senior : 
Has smoked a pipe for about seven 
15 | 18 | : | 28 |Law | years. ‘Smokes about 5 pipes of Velvet 
| |Student [per day. 
«“ Junior Has smoked a pipe habitually for last 
16 16 24 |in 5 or 6 years. Smokes 6 or 7 pipes per 
uenpeereenes es pet) cer Agriculture’ |[sey-000 © ees eee ee 
Sophomore : d 
5 Smokes 3 pipes of Velvet or Tuxedo 
iy 18 ce 21 | Medical per day and about one cigarette. Has 
| Student smoked habitually for 4 years. 
| | Junior Has smoked regularly f bout 4 years 
5 gularly for about 4 years. 
18 18 a A eatin Now smokes about 3 pipes and 4 ciga- 
| Agriculture |rettes per day. 
Has smoked regularly for about 7 years 
19 | 18 | “ 9 pee ore except for 1 year due to the objection of 
5 etters his father. Smokes about 5 pipes per 
| & Science |day of Prince Albert or Edgworth. 





24 CLARK L. HULL 


is supposed by the subject to be the drug in question. Few, however, 
have adopted the obvious precautions which such considerations 
suggest; Schumberg and Sobieranski are the only workers with 
drugs who have used any kind of control-substances, and even 
they do not make it clear that the control mixtures or injections 
they use were entirely indistinguishable from those containing the 
active substances. 

“The factor which previous writers have considered under the 
title of ‘suggestion’ is far from being the only source of error in 
work on the action of drugs. Féré has shown that the sensory 
stimulation involved in the act of taking a drug into the mouth 
and swallowing it may have a very decided effect on the amount 
of work executed with the ergograph, but even this knowledge did 
not lead him to adopt any control in his numerous researches on 
drugs. 

“There is, however, another factor which is probably more im- 
portant than either sensory stimulation or suggestion—viz., the 
interest and excitement produced by taking a substance when the 
discovery of its effect is the motive of the whole experiment. .. . 
Any novelty in the course of an experiment may have a very de- 
cided effect on the amount of work. The interest of a conversa- 
tion, the knowledge that the performance is being watched... . 
or any other variation in the routine of the daily experiment, may 
have very obvious effects on the amount of work. Similarly, the 
knowledge that it is the first or last day of an experiment may 
produce a distinct increase in the amount of work, so decided that 
I now always adopt the procedure of working for one or two days 
before and after the period which is to provide the proper data 
for the experiment. ; 

“Tf such a condition of interest as that arising from its being 
the first or last day of an experiment. . . . can have very appreci- 
able effects on the amount of work, it is clear that so interesting 
an occurrence as the administration of a drug must have a decided ° 
influence.” (Rivers, “The Influence of Alcohol and other Drugs 
on Fatigue,” pp. 18-19.) 

It is easy to show that without an adequate control, the results 
of tobacco experimentation may be almost meaningless. In one 


THE INFLUENCE OF TOBACCO SMOKING 25 


series of observations, the pulse of nine smokers was taken system- 
atically over a period of about 230 experimental hours. Each sub- 
ject’s pulse was taken (sitting) upon his first entering the labora- 
tory. After sitting quietly for 15 minutes, it was taken again, Then 
followed about 30 minutes of mental testing including five minutes 
of continuous addition, after which the pulse was again taken. 
Then came 25 minutes of smoking after which the pulse was taken 
a fourth time. Following this the mental tests were repeated three 
times more, after each of which the pulse was taken, making seven 
times in all. The last pulse was taken about 1 hour and 45 minutes 
after the conclusion of the smoking. The results of all nine sub- 
jects averaged together are shown graphically in Fig. 1. This 
curve shows a marked rise immediately after the dose. The ques- 
tion at one presents itself as to how much of this increase is due 
to the tobacco and how much to other factors? How much, for 
example, would the heart rate have increased merely as the result 
of the subjects’ puffing on the pipe, their expectation of some kind 
of an effect taking place and the interest and excitement of having 
the effect measured? We can not tell. Thirty-five minutes later the 
situation is even worse. It is impossible at this point to judge 
whether the tobacco has produced any effect whatever, to say 
nothing of how much. The pulse appears to have returned to 
normal. Again, at the end of the experimental day, the same am- 
biguity exists, though here the great fall in the curve suggests 
that the initial stimulation of the heart rate may have given place 
to a depression. The interpretation of the curve is thus largely a 
matter of conjecture. These data can only have value for scientific 
purposes when we know what would have been the heart rate 
throughout, had all other factors both physical and psychological 
been strictly the same except that no tobacco was taken into the 
body. This obviously can be brought about only by the use of a 
satisfactory control dose. 

Since the work of Rivers, the above principles have been general- 
ly recognized by psychologists. Nevertheless, Rivers himself con- 
ducted an experiment on the effects of smoking without any con- 
trol dose whatever. The reason appears in his rmark, ‘Any kind 


26 CLARKeLA BULL 


Number of heart beats per minute 





1 2 3 4 5 6 va 
Number of test 


Fic. 1. The average heart rate of a group of habitual smokers at various 
periods before and after smoking. 


of a disguise was of course impossible.’ Johnson came to the same 
conclusion ten years later. He says, “Unlike other experiments on 
the effects of drugs, it was impossible to disguise the taking of it 
into the body.’’® Froeberg, indeed, attempted a control dose but 
abandoned it. This particular defect in the technique of previous | 
investigators thus appears to have been due largely to the supposed 
impossibility of providing a satisfactory control dose. 


BOp cit. p. 114 
6 Op. cit., p. 130. 


THE INFLUENCE OF TOBACCO SMOKING 27 


Fortunately it was found possible in the present investigation 
to surmount this difficulty. After some preliminary experimenta- 
tion, a very satisfactory control dose was devised, though its use 
demanded some skill and deftness on the part of the experimenter. 
Indeed the success of the control depended as much upon the meth- 
od of use as upon the nature of the device itself. The first and most 
important consideration of method was that the subjects were 
never given the least inkling that a control dose was to be used.' 
To this end it was necessary deliberately to mislead them to a cer- 
tain extent, as to the real nature of the technique. In a series of 
two preliminary talks in which each subject was given his general 
instructions, it was explained among other things that the effects 
of the tobacco upon mental efficiency would be shown by the differ- 
ence between the scores on the tests before and after smoking. 
This seems quite logical to the layman. Accordingly (it was ex- 
plained) it was imperative that the subject should give the same 
conscientious application to the mental tests throughout the ex- 
perimental period. It was pointed out with great earnestness that 
the success of the entire undertaking depended upon this. If, for 
example, there should be any letting down of the subject’s efforts 
after smoking (it was explained), this would decrease the score 
at that point and would falsely be taken as an evil effect of the to- 
bacco, thus completely invalidating the experiment.* To emphasize 
this still further, before each subject was engaged, a solemn prom- 
ise was exacted from him to keep up throughout the experiment 
the maximum effort that could consistently be maintained. The 
great earnestness with which this “‘coaching” was done seems to 
have had much to do with the success of the control dose. 

Moreover, the technique of the smoking itself was designed in 


7 The importance of this factor can scarcely be overestimated. Some drug 
investigators seem to have overlooked it entirely and their subjects appear to 
have been constantly on the alert to see if they could not detect the control. 
Nothing could be more unpsychological. The present device would. probably 
have failed completely under such conditions. 

8 While such a method of experimentation as described to the subjects would 
have been without scientific value, it was not so very different from some 
actual drug experiments that have been reported. Only one subject of the 
nineteen saw through the deception. His results were thrown out for this rea- 
son. (See note, p. 31.) 


28 CLARK UT: -AUELL 


part to facilitate the use of the control. On approximately half of 
the experimental days (which always included the first two of each 
man’s series) the subjects smoked the regular tobacco in a regular 
pipe, blindfolded. The preliminary talks had prepared the subjects 
for a very elaborate technique, and the blindfolding caused no sur- 
prise. After the experimenter had filled the pipe in preparation for - 
lighting on the first day with a given subject, he explained to the 
man in a somewhat technical manner, that there was some scien- 
tific reason to believe that even the sight of the smoke might have 
an influence on the results entirely apart from any physiological 
effect the tobacco itself might have. This (it was explained) would 
obviously spoil the experiment. He was therefore asked to close 
his eyes and keep them closed throughout the smoking period. 
After the subject’s eyes were closed, the experimenter casually 
added, “In order that you shouldn’t forget at any time, I'll just put 
this over your eyes to prevent any accident.’ With this he quietly 
adjusted over the subject’s eyes a heavy blindfold specially pro- 
vided with pads to fit either side of the nose. The necessity of 
exactly timing the puffs was also explained. Owing to the sub- 
ject’s inability to see the watch, the experimenter handled the pipe, 
putting it to the subject’s lips for three puffs every 20 seconds. 

On the remaining experimental days but entirely unsuspected 
by the subjects, the regular tobacco pipe was replaced by a special 
experimental pipe. The second pipe was originally an exact dupli- 
cate of the first. (Plate 2). In its bowl was installed an aluminum 
capsule with walls two millimeters in thickness. The top of the cap- 
sule projected three centimeters above the wood of the bowl. In the 
bottom of the capsule was placed some porous asbestos plaster 
through which a small hole led downward through the capsule it- 
self to near the opening which leads out to the stem of the pipe. 
Above the plaster and resting in a cup-shaped depression of the 
latter, were two concentric asbestos insulating tubes, the outside 
diameters of which were 1 centimeter and .35 centimeter respect-’ 
ively.° Between these tubes wasacoil of 25 turnsofnicrome electric 


9 The asbestos tubes were made by moistening rather liberally a piece of thin 
asbestos paper of proper dimensions and wrapping this about a smooth round 
metal rod of suitable size. The wrapping was done by rolling the rod over the 








xu #30 


PLATE 2. The special experimental pipe (above) and the regular tobacco pipe 
(below). Note the exact similarity in form of the two pipes. 







; HW itah At 
ma ah id .a0 


ey tee 
| | ae 








‘ 
j 
| b 
mh 
i “hy 
‘ ty 
4@ 
ral 
ae y 
Tie) 


THE INFLUENCE OF TOBACCO SMOKING 29 


heating wire, 1% millimeter in diameter. The wire from the lower 
end of the coil returned upward within the smaller insulating tube. 
The two ends of the wire, well apart, now arched upward from 
the tubes, over the edge of the capsule and thence downward, each 
to a separate binding post screwed into the bowl of the pipe. 
(Plate 3). A direct current of suitable size was led to these posts 
by flexible lamp cord, from a rheostat receiving 110 volts. A few 


Cc 










» 


ESSA WAS Hg 









Wid da ddbddsdiddaadlddfs 


MULL 


PLATE 3. Diagram of experimental pipe. A, aluminum capsule; B, outer 
asbestos tube; C, inner asbestos tube; D, plaster moistened with water; E, 
hole through moistened plaster through which heated air passes. 


drops of water placed carefully on the asbestos plaster about two 
hours before use so as to be thoroughly absorbed, completed the 
device. 

The warm, slightly moistened air obtained by the subject from 
this experimental pipe, then, furnished the basis for the illusion. 


paper (once one edge of the paper is made to adhere to the rod) with a heavy 
downward pressure. After heating a short time while still on the rod, the tube 
becomes very firm if sufficiently wet before heating. The paper used by the 
writer was made by himself from asbestos fibres washed from some asbestos 
plaster and dried in a thin layer. 


30 CLARK, LA sHULE 


The temperature of the air could be controlled at will by the ex- 
perimenter through the adjustment of the rheostat. In addition, 
the resistance to suction as well as the sound of the air being drawn 
through the device, were carefully adjusted by means of asbestos 
fibre, to duplicate the corresponding aspects of actual smoking. 
The feeling of the stem in the mouth was an exact duplicate. Near 
by but unknown to the subject, the experimenter himself smoked 
more or less on the real pipe and with the real tobacco, thus fur- 
nishing the indispensable odor.*® And since there probably is no 
taste in tobacco smoke" the only factor of the normal smoking 
complex lacking, is the occasional slight bite of the tobacco on the 
tongue. A little excess heat easily furnished this last necessary 
element of pain. wi 
In addition to the above synthetic duplication of the sensory ex- 
perience of smoking, the whole thing was powerfully reinforced 
by normal suggestion. When the subject took his place in the 
smoking laboratory, he saw the familiar (regular) pipe, tobacco, 
and matches in their usual places. A quantity of strong-smelling 
charred tobacco from previous smokes was strewn about on the 
table in an untidy but extremely suggestive manner. Before the 
dose on the control days, the experimenter would elaborately (but 
without remark) clean out the real pipe in the subject’s presence, 
thus furnishing him with an explanation should he notice any 
difference in the “strength” of the pipe on that day. After being 
blindfolded, he heard the tapping of the tin, and other incidentals 
to the filling of the pipe, the striking of the match and the fragance 
of freshly lighted tobacco came to his nostrils exactly as on the 
tobacco days. And when the smoking was over, he saw the charred 
remains of the tobacco in the real pipe (which unkown to him the 
experimenter had been smoking) there before his eyes. Even the 
details such as the steps taken and pauses made by the experimenter 
in securing the experimental pipe from its hiding place, the attach- 


10 This was often discontinued in the latter part of a given smoking period 
as the olfactory organs grow insensitive to an odor after it has continued for 
some time. 

11 For the benefit of the non-technical reader, it may be stated that we are 
able to taste only sweet, sour, bitter and salt. The rich variety of flavors in 
foods and tobaccos are due chiefly to smell. 


THE INFLUENCE OF TOBACCO SMOKING 31 


ing of the electrical connections and so on, were also gone through 
with on the tobacco days so that there should be no avoidable 
difference whatever between the control and the tobacco days. On 
the top of all, the subject’s attention was diverted from the smok- 
ing on all days alike by gossipy conversation. 

Under these conditions, confirmed smokers would puff the warm 
air with apparent satisfaction and even (as in one case) serenely 
go through the motions of blowing smoke rings! In a number of 
cases where the attempt was made at the conclusion of a series, it 
was actually found difficult to persuade subjects verbally that they 
had not been smoking on every experimental day. When shown 
the experimental pipe they could hardly believe their eyes and de- 
clared that after they knew what it was, it did not “taste” the same 
as it had a minute or two before when they did not know. In the 
course of the introspections taken at the conclusion of each sub- 
ject’s series, practically all of the eighteen subjects stated positively 
that even though they were blindfolded and could not see the 
smoke, they could tell the pipe was lit because they could feel the 
“smoke” in their mouths on every one of the experimental days. 
Nearly all of them stated further that it would be impossible to 
persuade them to the contrary.’? We have here, in short, a repeti- 
tion of the psychology of the man smoking in the dark who doesn’t 
know that the pipe has gone out. Indeed this was the clue upon 
which the method was originally based. 

The adequacy of the control dose was regarded as of such fun- 
damental importance that a very careful introspection on this 
point was obtained from each subject at the close of his part of the 
experiment. The introspection was taken down by the present 
writer in long hand, then read to the subject for the correction of 
any errors, after which is was signed by the subject and filed. 
These documents not only attest the perfection of the illusion pro- 
duced by the control dose but also yield extremely interesting sug- 
gestions as to the general psychology of the attractiveness of smok- 


12 One subject (No. 14) grew suspicious and on one of the control days 
early in his experimental series removed his blindfold and probably saw the 
experimental pipe. Thereafter the control dose failed to deceive him and his 
results were accordingly thrown out. They are given in Appendix J. 


32 CLARK L. HULL 


ing. A characteristic one is that of subject No. 12, habitual 
smoker :— 


S (subject) thinks that if he inhaled the smoke, there wouldn’t 
have been any difference in the laboratory from ordinary pipe 
smoking. As it was, the only way he could tell he was smoking 
was by the gradual increase in the strength of the smoke and the - 
bite on his tongue. S sometimes told he was smoking by the smell 
but usually does not smell tobacco much. S was able to tell at all 
times that he was smoking. There were several times that he could 
not tell whether the pipe was going or not. Such periods were for 
three or four puffs. S was always sure he was smoking the most 
of the time on every evening. There was never any evening when 
he could have been persuaded that he had not been smoking at 
last ninety-five per cent of the time. S thought that some nights 
there was little or no stinging on the tongue. On such nights he 
told by the flavor. The last night of the experiment (a tobacco 
night) it was so strong S did not like it. It bit his tongue and it 
was an effort to take another pull. The night before, however 
(a control night) it was fairly good. It didn’t bite the tongue to 
any great extent, not enough to bother much. Jt would be an easy 
matter for S to break off smoking tf it were always like the last 
night. S enjoyed it the night before. It wasn’t strong at all. It 
tasted fairly well and took the place of not being able to inhale. 
S thinks it would be pretty hard to quit under such (control) con- 
ditions. (Signed) A. M. G. 

The above introspection is particularly striking in that it shows 
a smoker preferring the control dose of warm moist air to the 
genuine tobacco and feeling that it increased the strength of the 
habit! The next introspection, that of subject No. 15, habitual 
smoker, is given because it is the only case where a real doubt 
entered the mind of the subject. It will be observed that this doubt 
was a sort of after thought as shown by the somewhat contradic- 
tory statement following the second italics. This statement was 
brought out by a definite question as to whether it would be pos- 
sible to persuade him that he had not been smoking on any of the 
nights :— 


S always felt rather hungry for a smoke when he first came to 
the laboratory. But after the smoke in the laboratory he was always 
satisfied. S says that he did not enjoy the smoking, though, when 
it was going on. This was probably because he couldn’t see or 
handle the pipe. It was given to him slower than he was accustomed 


THE INFLUENCE OF TOBACCO SMOKING 33 


to taking it. S thinks it very difficult to tell while blindfolded 
whether he is smoking or not. S has wondered lots of times whether 
the pipe wasn’t pretty near out. These periods were for three or 
four minutes. But this can’t be true because he heard experimenter 
light the pipe. There was never any night when S was in doubt as 
to whether the pipe was lit throughout the evening as a whole. 
S thinks that on one evening one might persuade him that the pipe 
was not lit. S never wondered about the matter except this one 
night. (Signed) G. W. M. 

A third introspection will be given as typical of the non-smokers. 
This is from subject No. 7. This subject was somewhat apprehen- 
sive about entering upon the experiment because of fear that he 
might acquire the smoking habit against his will. He was there- 
fore on the alert for any symptoms of habit formation. Thus 
came about the extremely curious observation of the habit-form- 
ing tendencies (under the influence of suggestion) of ““smoking”’ 
warm moist air. 

On some of the nights when it was not very strong S rather 
liked the smoking. This was strongly apparent about the eleventh 
day. On this day (evidently a control day) S felt that if he had 
not moral prejudice against smoking that he would rather like 
to do it voluntarily. This grew slightly stronger until the end 
of the experiment. Last night (a control night) it was best 
of all. S feels that such satisfaction as last night constitutes a real 
habit but not too strong to be overcome. Tonight, however (a to- 
bacco night) he did not enjoy it and would not have smoked by 
preference. 

S was always sure that he was smoking from the combination 
of sharp stinging sensation and a ticklish sensation. Always had 
this on every night. S could always feel the smoke in his mouth. 
There was never any time even for a single puff when S doubted 
that he was smoking. Jt would not be possible for any one to per- 
suade S that he was not smoking any of the time. 

(Signed) E. H. 

With a suitable control dose, it is now possible to secure data 
which will enable us to interpret with confidence the pulse curve 
which previously baffled us. These supplementary data are re- 
presented by the broken line in Fig. 2. They were obtained from the 
same nine subjects as before, only this time they smoked nothing 
but warm air. Since they fully believed they were smoking tobacco, 


34 CLARK CX HULL 


80 


70 


60: 






per minute 
8 § 


8 


Number of heart beats 
i) 





i 3 


2 
Number of test 
———- Tobacco days =--=-Control days 


Fig. 2. The average heart rate of a group of habitual smokers on tobacco days 
and control days. The amount of separation of the curves after aoe in- 
dicates the tobacco effect. 


suggestion, interest, excitement, personal bias for or against to- 
bacco, states of tension or relaxation, processes of digestion, and 
any other obscure diurnal rhythms, are all constant. Previous to, 
the dose the curves are seen to follow an identical course. Had no 
dose been taken we may assume that they would have continued 
to do so. After the dose they diverge. We can now say with ap- 
proximate certainty that the smoking caused an increase in the 


THE INFLUENCE OF TOBACCO SMOKING 35 


average pulse rate of these subjects, of a little over seven beats 
per minute. Moreover, instead of the stimulation disappearing at 
the end of 35 minutes as might have been supposed from Fig. 1, 
we find that nearly 70% of it still remains. And at the end of 134 
hours, where a reversal of the influence seemed certain from Fig. I, 
we find as a matter of fact that the stimulation still retains over 
40% of its original intensity ! 

Similar curves illustrating the same principle but based upon a 
variety of other functions appear in Figures 11, 14, 15, 16, and 17. 

The decision as to the number and the type of mental and neuro- 
muscular processes to be investigated, present certain difficulties. 
A drug may affect different functions quite differently. For this 
reason as well as from the point of view of the number of com- 
parisons possible the more functions investigated the better. On 
the other hand, in tracing the course of a changing process such 
as the waning effects of a drug, it is desirable to locate as many 
points on the curves as possible in the allotted time, lest we miss 
some important transitory phase of the action. This is particularly 
true of the period immediately following the taking of the drug. 
But obviously the first test of a series is the only one that strictly 
tests the immediate effects of a drug, and the last test of a long 
series may even miss the effect entirely. From this second point of 
view, then, the shorter the series the better. These two conflicting 
points of view can be reconciled in part by a series of tests fairly 
large in number but capable of being given in a fairly short period 
of time. This means that the individual tests should be very brief 
and that no very lengthy test can be used at all. A list of twelve 
mental and neuro-muscular functions was finally adopted. Fortu- 
nately it was found possible so to devise the tests that in several 
cases two fairly distinct functions could be measured simultane- 
ously. Partly owing to this, it was possible without haste, to give 
the entire series in 30 minutes. 

The functions finally selected for investigation are listed below 
in the order of the increasing complexity of the neurol processes 
involved, and indication is given of the method used in measur- 
ing each: 

1. Heart rate, measured by counting the radial pulse. 


36 CLARKEERAU LL 


2. Tremor of the hand and arm, measured by Whipple’s stead- 
iness test. 

3. Rate of voluntary movement, measured by the speed of 
tapping with a telegraph key. 

4. Muscular fatigue, measured by the decrease in speed which | 
results from continuous tapping. : 

5. Rate of discriminatory eye-hand reactions, measured by the 
speed of cancelling A’s. | 

6. Accuracy of discriminatory eye-hand reactions, measured 
by the number of errors in cancelling A’s. | 

7. Rate of eye-voice reactions which are based on old estab- 
lished associative bonds, measured by reading reaction-time. 

8. Rate of eye-voice reactions which are based on recently 
formed associative bonds, measured by learning reaction-time. 

9g. Rate of continuous associative thought, measured by the 
speed of continuous mental addition. 

10. Accuracy of continuous associative thought, measured by 
the accuracy of continuous mental addition. 

11. Facility in the formation of short-lived associative bonds, 
measured by the auditory memory span for digits. ) 

12. Rate of learning (formation of relatively permanent as- 
sociative bonds), measured by the speed of memorizing non-sense 
material. 

The order of the tests as administered to the subjects was de- 
termined after a preliminary series of experiments with four sub- 
jects, the results of which were discarded. The sequence finally 
chosen was the one which seemed to offer the most favorable op- 
portunity for the various tests to yield reliable measures. It was 
as follows: 

Pulse 

Adding 

Memory span 
Steadiness 

A-test 

Reading reaction-time. 
Memorizing 


Tapping 


a Nee 


THE INFLUENCE OF TOBACCO SMOKING 37 


Since neither pulse, adding nor memory span required the use of 
the eyes, these tests were placed first in the series to avoid any evil 
effects from the dark adaptation of the eyes following the removal 
of the blindfold after smoking. Steadiness was placed some dis- 
tance from tapping to avoid increase of tremor likely to arise from 
the latter activity. Tapping was placed last so that no test what- 
ever could follow it immediately. The reason that eight tests ap- 
pear in the above list rather than twelve is that four of the tests 
give a simultaneous measure of two functions each. 

The typical routine of a smoker subject’s day may now be sum- 
marized. He went about his daily tasks as usual, carefully avoid- 
ing any unusual exercise or exertion and any alcoholic drinks or 
unusual foods. His smoking habits were not disturbed except 
that he agreed not to smoke during the three hours immediately 
preceding the experiment. Otherwise his smoking and, so far as 
possible, all the other activities of his life were to be kept as con- 
stant from day to day as possible. He finished his evening meal at 
about 6:25 and reported at the laboratory at 6:50 p.m. : 

6:50 Pulse taken after which subject sat quietly for about 15 

minutes. 

7:05 Complete series of tests given as listed on p. 36, requir- 

ing 30 minutes. This is the normal of the day. 

7:35 Pulse taken after which eight minutes were consumed 

in preparation for the smoking. 


7:45 Began either smoking or taking the control dose, which 
lasted 25 minutes. 


8:10 Experimenter puts away tobacco. 
8:12 Complete series of tests repeated. 
8:42 Subject rested for 5 minutes. 
8:47 Complete series of tests repeated. 
9:17 Subject rested for 5 minutes. 
g:22 Complete series of tests repeated. 
9:52 Pulse taken. 

9:55 Subject excused. 


The results of the first day of experimentation with each sub- 
ject were always discarded as a practice or shock-absorber series, 


38 CUARKVLVAGLY 


though the subjects naturally were not informed of this.** There 
remained the results of 17 days which were available for statistical 
treatment. Of these, 9 were smoking days and 8 were control days. 
The sequence of the two types of days was a somewhat complex 
alternation designed both to neutralize any constant tendency to 
error due to practice effects and to avoid arousing the suspicions 
of the subject that any kind of alternation whatever was being 
used. The sequence employed in nearly all cases was as follows: 


Smoke (thrown out) 
Smoke 
Control 
Smoke 
Control 
Control 
Smoke 
Control 
Smoke 
Smoke 
II. Control 
12. Smoke 


DEG pf OUe NOS a 


_ 


12... Control 
14. Control 
I5. Smoke 
160. Smoke 
17...) Control 
18. Smoke 


The above order was varied somewhat in a few cases where the 
subject was unable to complete the entire series of 18 days. The 
braces indicate practice-neutralizing groups based on a principle 
of symmetry, though the first group is not quite perfect. It will 
be shown in another connection, however, that practice errors were 
probably completely neutralized by another feature of the tech- 
nique. 

The experimental results must also be guarded against tenden- 


138 With two or three of the early subjects the second day was also thrown 
out but this was later found to be unnecessary. 


THE INFLUENCE OF TOBACCO SMOKING 39 


cies to end spurt and other characteristic disturbances of the last 
day or two of experimentation resulting from the excitement of 
the subject over the fact that he has reached the end of a long and 
arduous experiment. These disturbances have been emphasized by 
Rivers.** They were easily avoided in the present investigation by 
engaging the subjects for 20 days and then excusing them at the 
conclusion of the work on the eighteenth day, two days before 
they had expected to finish. 

The basic principle underlying the method of determining the 
effect of the tobacco on mental and motor efficiency, has been sug- 
gested above in a general way (pp. 26 and 34) by the discussion 
of the pulse rate in connection with the use of the control dose. 
The results on the control or non-drug days establish a standard 
or normal performance. If the results of the drug days follow, on 
the average, the same course as the standard performance, then 
we must assume that the drug has no effect whatever. If, on the 
other hand, the performance on the drug days deviates on the 
average from the standard performance more than chance ex- 
perimental errors would ordinarily produce, we must assume that 
this deviation is caused by the tobacco. This is the fundamental 
principal upon which modern drug experimentation is based. 

The principle of a standard performance was reinforced by a 
second principle, that of the normal test of the day. It has already 
been pointed out (p. 37) that both on the tobacco and on the con- 
trol days, the tests were given once each day previous to the dose 
and three times after it. The test previous to the dose in each case 
is called the “normal of the day.’’”’ It is obvious that people are 
more vigorous and efficient on some days than on others. Practice 
effects in particular often cause the score on later days to be 
definitely higher than those of earlier days. If these practice effects 
were unequally distributed among the tobacco and the control days, 
they might easily produce an appearance of a drug effect where 
there is none at all*® or indeed mask an effect which really exists. 
It is accordingly necessary to have a normal performance at the 


14 See page 24 above. 
15 Dodge and Benedict, Psychological Effects of Alcohol, p. 28. 
16 See Berry’s results on errors in addition, Appendix F. 


40 CLEARKVLVHOLE 


beginning of each experimental day to indicate the general level 
for that day. Once this is known, the results of the test following 
- the dose can be expressed in terms which will be independent of 
this disturbing factor. The customary way of doing this is to 
tabulate the results of all the tests following the dose in terms of | 
this normal of the day. Thus, immediately after the dose, a sub- 
ject will be recorded as so much more (-++) or less (—) efficient 
than before. The drug effect is then determined by comparing the 
average gain or loss in efficiency after the tobacco dose with that 
after the control dose. For example, if a given subject immediately 
after the control dose should average more efficient by 5 points, 
and after the tobacco dose, less efficient by —4 points, it is clear 
that the subject is less efficient by —9 points after smoking than 
he would have been had he not smoked, and irrespective of the 
accidental levels of efficiency originally characteristic of the two 
groups of days.*’ 

The details of the method of determining the effects of smoking 
on mental efficiency which will be used uniformly throughout the 
present monograph, are illustrated in Table II. This shows the 
results on the adding test of subject No. 7 a non-smoker. It should 
first be noted that the table consists of three horizontal sections 
which are divided vertically into eight columns. The horizontal 
sections are devoted respectively to the results on the control days, 
the results on the tobacco days, and (at the bottom) the final net 
effect of the tobacco. In the first four of the columns (1, 2, 3, and 
4) are recorded respectively the number of correct additions per- 

17 The above discussion neglects to consider the effects of practice from one 
test to the next on a single experimental day. It is assumed that the gain from 
this source will be equal for both the tobacco and the control days. This assump- 
tion is slightly complicated by the fact that practice curves are not straight but 
have a negative acceleration. The method of frequent alternation of smoke 
and control days was intended largely to eliminate this factor, as on any short 
segment of the practice curve it is practically straight. Any inequality still re- 
maining will be equalized by the special practice-equalizing grouping of days 
of the type A. B, B’, A’ (p. 38). If A is slightly larger than B or B’, then A’ 
will be correspondingly smaller than B or B’ and the average of the two A’s 
will be approximately that of the B’s. As an added precaution, one of the 
groups is arranged in the order B A A’ B’. Hollingworth, in his work on 


caffeine, sought to eliminate the disturbing effects of practice by a preliminary 
period of training. This really eliminated only the first part of the curve. 


THE INFLUENCE OF TOBACCO SMOKING 41 


formed during the four tests of each experimental days. In the 
next three columns (5, 6, and 7) are shown with appropriate signs, 
the gain or loss in efficiency over the normal of the day, of each of 
the three tests following the dose. The last column (8) gives the 
average net gain or loss in efficiency on the three post-dosage tests 
recorded in columns 5, 6, and 7. A plus sign always means a gain 
in efficiency or a stimulation and a minus sign a loss in efficiency 
or a depression. 

To illustrate: On March 17, a control day, the subject per- 
formed 166 correct additions before the dose (the normal of the 
day) and 175 immediately after the dose. This is a gain of (+) 9 
points in adding efficiency and as such is recorded in column 5. On 
test III (40 minutes after the dose) he made 186 correct additions 
which is (+) 20 points more efficient than the normal of the day 
(166), so 20 appears in column 6. On test IV, an hour and a quar- 
ter after the dose, he performed 172 correct additions which is a 
gain in efficiency over the normal of the day of 6 points. This is 
recorded in column 7. The three post-dosage tests thus scored for 
efficiency show an average gain of (+) 11.6 points. This is re- 
corded in column 8. 

The average gain or loss in efficiency for a given post-dosage 
test on a given set of experimental days, is found by adding alge- 
braically the efficiency scores in appropriate column and averaging. 
These averages are shown in special type. Thus the first post- 
dosage tests on the control days (column 5) average a gain in 
efficiency of 2.4 points, whereas the corresponding test for the to- 
bacco days averages a loss of —5.5 points. The subject therefore 
was less efficient in addition after smoking than after the control 
dose, by —7.9 points. This, then, within the limits of experimental 
error, is the final net effects of the tobacco, and as such is recorded 
in the appropriate column (5) of the third and lowest section of 
the table. The percent of gain or loss in efficiency is computed on 
the basis of the average of the means of the normal tests of the 
day of the control days and the tobacco days respectively. In the 
record under consideration, one mean is 222.5 and the other 226.9, 
which yield an average of 224.7. By simple division, —7.9 is found 


42 


CLARK -LSHOULE 


to a 3.5% loss in efficiency and as such is recorded at the bottom 


of column 5. 


The nature and the size of the difference having been found, it 
is next necessary to determine whether this difference is probably 


TABLE II 


Adding, subject No. 7, non-smoker. Score, nwmber of correct additions per- 
formed in five minutes. Plus means a gain in efficiency as result of smoking, 
minus means a loss. 


Difference between normal of day 


(1) (2) (8) 
Test Test Test 
Control I II III 
days: (Normal) 
Maree 66500175.) 86 
sey 1 Oona OSia 1 947 15200 
a2 OM tet 9 Some Sogn OS 
omer Sealers tal Oss 
AMPA YW) Ay EST aries 
i eo Ome 4 ONS 25 a2 OG 
NONLIN EZ6S PMZos 4 asd: 
Hee ahi n el ees PA Pay ZL! 
Total 1780 1799 1875 
Average 222.5 224.9 234.4 233.2 
NDS Milita | ateiec ene erie acorn reece aloe ie 
Be Ene, wis cud asi loka eae dere oS 
Tobacco 
days: 
Mar.16 143 154 £4150 
SON GES UR al Gy ener 
olan ee O0teee 97a ul ob 
Apa ay BP aDA ey ANIA Pepa 
24 eC oSeeT oS eaOO 
BP PAE CASS GRAY EVA 
Se pA PAR BAT 9 DIRS 
PTL PAPA DAP OLD: 
Apr. 1) 266. 5260 270 
Total 2042 1922 2018 
Average 226.9 221.3 224.2 223.5 
AEA Al Ayah Pie ataks Ate ts itd we Aa (tO ie 
PU EME Seley es ont aeaine Be ee ae ee toes 
Effect of 
Tobacco: 
Differenceitpea tis re ace nia ee. eae ie 
Ratighi, 22.bh eaiv irene lece wae de 


Rela bunyy ; dora swat oasis eee 
Per cent gain or loss 


Original scores 


(4) 
Test 
IV 


172 
190 
216 
207 
257 
256 
282 
286 


1866 


(5) 
Test 
II 


8.39 


and subsequent tests 


(6) (7) (8) 
Test Test Average 


Ill IV difference 
ate ape te +11.6 
7 — 3 + 1.6 
aa +18 kG 
—1l11 — 2 — 1.3 
+31 +15 +19.3 
+26 +16 +15.0 
+12 uid CUS 
+15 +23 +13.0 





+95 +86 +666 
+119 +107 4838 





11.15 7.82 6.4 

3.32 2.33 1.91 
7 A + 7.3 
13 ere — 5.0 
zayT ais 10.3 
+9 23 +10.0 
ee 5 + 3.6 
aore +7 — 2.0 
9 + 4 + 2.6 
—20 2336 —28.3 
+4 eis — 6.6 
—24 —12 —28.7 


—14.50 —12.00 —11.50 
4.17 4.25 3.02 
3.47 2.82 3.80 

.990 971 995 


— 35% — 64% — 5.3%. — 5.07% 


THE INFLUENCE OF TOBACCO SMOKING 43 


caused by the tobacco or is the result of accidental factors. The 
issue depends upon the size of the difference found in relation to 
its probable error (P. E.p).** The general characterictics of this 
dependence will become evident upon a little consideration. If with 
a small number of measures upon a given subject, we should find 
that the tobacco days averaged the same as the control days, it 
would not necessarily mean that the tobacco had no effect what- 
ever on adding efficiency. With an indefinitely large increase in 
the number of measures, the two averages might turn out to be 
perceptibly different. Now it is obvious that in advance of trial, 
such a change is as likely to be in the direction of a loss in efficiency 
as of a gain. That is, out of 1000 chances there are 500 that the 
true average is in reality a loss of greater or less amount, and 500 
that is a gain of greater or less amount. But, in case the averages 
from a limited number of measures yield a difference indicating 
a loss in efficiency say, and as great as the P. E.p, then the chances 
that an infinite increase of the measure would reveal a loss as the 
true average, is increased from 500 chances to 750 in 1000. The 
chances of its revealing a gain in efficiency is correspondingly de- 
creased to 250. Or, if the difference found is twice as large as the 
P. E.p and in the direction of a loss, then the chances that the true 
average from an infinite number of measures will show a loss is 
increased to 911 with only 89 chances that it will show a gain. 
Thus the larger the difference found in proportion to the P. E.p, 
the greater the probability that the true difference is at least in the 
same direction as found, and the less the chance that it is in the 
opposite direction. 

18 For the benefit of the non-technical reader the process of arriving at the 
P. E.p may briefly be indicated. The mean variation (M. V.) of each of the 
two sets of scores (as in column 5) is determined by first finding the algebraic 
difference between each item in a given set of scores and their average. The 
average of these differences is called the M. V. The probable error of the mean 


or average of a given set of scores (P. E.y) is next computed by the formula 


8 M. V. 
Pe E.m = Sera 


average was computed. Lastly, if we call the probable error of the mean of the 
control days, P. E.y,, and that of the tobacco days P. E.m., the probable error 
of the difference between the two averages is computed by the formula: 


P.E.p=//P. Em, + P. EM, 


where N is the number of scores from which the 


44 CLARK LWHOULL 


The following table summarizes these various relations in a 
systematic manner. This shows that with a difference as large as 


Taste III 
Differences between Number of chances in The chance that _ 
averages (assumed to 1000 that the true the difference 
show a loss if greater average will show found will be 
than zero) | | reversed 
| a loss | a gain | 

Of Zero | 500 | 500 | Lin2 
As large as the P. E.p | 750 | 250 | 1in4 
Twice the P. E.p | 911 | 89 | 1in10. 
Wad th oo teh ANE NO IO Ly 
Three times the P. E.p | 979 | 21 | 1in 47 
Four times the P. E.p | 997 | 3 | 1 in 285 
Five times the P. E.p | 999.6 | 4 | 1 in 2632 
Six times the P. E.p | 999.97 | .03 | 1 in 33,333 


6 time the P. E.p, complete certainty is not obtained. Theoretical- 
ly even here, there is one chance in some 33,333 that the true | 
difference would be opposite to that found. Such a remote prob- 
ability is of course quite negligible as is also 1 case in 2,632. On 
the other hand one chance of a reversal in 2 or 4 is So great as to 
be altogether beneath serious consideration. The lowest reliability 
that is ever used to base action upon in practice is twice the P. E.p, 
which yields 1 chance of a reversal in about 10. A difference three 
times the P. E. p, which yields only 1 reversal in about 47 cases, is 
considered practical certainty. The smallest reliability to be con- 
sidered seriously in the present report unless supported by other 
evidence is 950, i.e., one yielding 1 chance of error in 20. 

It is customary to express the reliabilities of differences between 
averages as decimals of perfect reliability which is 1. Thus for a 


THE INFLUENCE OF TOBACCO SMOKING 45 


zero difference the reliability will be .500, for once the P. E.p it will 
be .750, for twice the P. E.p it will be .g11 and so on down the 
second column of Table III except that a decimal point is placed 
before the numbers as listed there. 

Applying the foregoing considerations to the results given in 
Table II, we find that the difference of —7.9 already noticed, has 
a probable error of 2.935 which is recorded beneath it in column 5. 
By division, the difference is found to be 2.69 times as large as its 
probable error. This is also recorded. By referring to a table giv- 
ing values of the probability integral for probable errors’® we find 
that 2.69 corresponds to 965 chances in 1000 that the true average 
would show a loss in efficiency. Assuming that the method of the 
experiment is sound this means that there is only one chance in 
about 28 that tobacco did not cause a loss in efficiency in this sub- 
ject. This is easily within the conventional limit of reliability 
adopted above as satisfactory. The reliabilites of the differences 
found on the second and third post-dosage tests are .g90 and .971 
respectively while that of the averaged data in column 8 is 995. 
This latter figure means that there is only one chance in about 200 
that the smoking did not have a detrimental effect on the subject’s 
adding efficiency throughout the period investigated. 

But the issue can not be settled by the results from a single sub- 
ject, no matter of how high a reliability. In drug action individual 
peculiarities are common. Our present interest is not primarily 
with idiosyncrasies but with characteristic reactions shared by 
people in general. The effect of tobacco for us, then must be de- 
cided primarily by the nature of the average effect obtained from 
a group of subjects representative of the general population of 
non-smokers and habitual smokers. And the reliability that in the 
end will be decisive will be the reliability of this average. Its de- 
termination will briefly be indicated in the next chapter. 


19 Thorndike, E. L., Mental and Social Measurements, p. 200. It will be noted 
that 500 has to be added to each entry in this table, since 500 chances are in 
favor of a loss, say, with a zero difference between the averages. 


CHAPTER 


THE EFFECT OF SMOKING ON THE HEART RATE 


Pulse rate was introduced into the present experiment after the 
first six non-smokers had been tested. The function in question is 
obviously physiological and only remotely psychological, though 
involving important neuro-muscular mechanisms. Preliminary 
observations on some of the early subjects, however, as well as the 
results reported by other investigators,’ had indicated that the 
heart rate is a rather sensitive and reliable index of the action of 
tobacco smoking on the human organism. It was accordingly in- 
troduced into the series of tests for purposes of comparison and 
also as a kind of control for such mental processes as should fail 
to show any reliable effects at all. The heart rate was determined 
by the simple counting of the radial pulse for one minute, the sub- 
ject sitting. The subject’s wrist was held for about 20 seconds be-- 
fore counting was begun in order that the slight excitement often 
arasing at such times, should have an opportunity to subside. A 
typical set of pulse data is shown in Table IV. They are the results 
from subject No. 15, habitual smoker.* The pulse was counted — 
seven times on each experimental day—three times before the 
dose and four times after. The detailed circumstances have been 
described above (p. 25) in connection with the account of the 
control dose. The average of the second and third counts was 
taken as the normal of the day and is recorded in the table as 
“Test 1.” The various computations have been made as outlined 
at the end of Chapter II. The table shows that with this subject all 


1 See above pp. 6-7. 

? Similar tables of the results from this subject will be used throughout the 
remainder of the present monograph for illustrative purposes. In this way it is 
hoped that the reader may secure a tolerably complete picture of a typical set of 
experimental results. A smoker was chosen for this purpose because the prob- 
lem of the effects of smoking on this group of subjects is more acute since they 
represent the part of the population which does the smoking. This particular 
subject was chosen because his results happen to agree with the average from 
his group better than the others. In this sense the hasty reader may consider his 
record as typical of the entire group. 


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48 CLARK L. HULL 


the postdosage tests yield a stimulation and all but one (including 
the average) have a satisfactory statistical reliability. 

As pointed out at the end of the last chapter, the results from 
one subject, no matter of how high a reliability, can hardly be 
taken as conclusive evidence of the nature and extent of the in- © 
fluence of a drug on a population in general, because people may 
differ in their reactions. We must accordingly test a group of in- 
dividuals chosen at random from the population. This presents a 
new statistical problem. In Tables II and IV above, the reliability 
of the final results was attenuated by the varying of a subject from 
himself on different days. This, in a measure, was compensated 
for by the large number of experimental days. We now find the 
reliability of the average results from a group of subjects suffer- 
ing from the variability of one subject from another in the nature 
and extent of his response to the drug. In this case compensation 
must lie in the large number of subjects tested. 

The final results of the present investigation as to heart rate are 
summarized in Table V and VI. It will be observed that these 
tables are constructed by merely assembling the essential data from 
the lowest horizontal section of the tables of the individual sub- 
jects, such as Table II. This will be clear to the reader if he will 
note the results of subject 15 as they appear in the third section of 
Table IV and as they reappear in Table VI. Thus, under each 
post-dosage period in Table VI, there appear both the absolute 
difference in heart rate due to the tobacco and the percentage ef- 
fect, together with the probable error and the reliability of the 
former. The two columns representing the effect of the drug are 
each averaged with due consideration of the sign of the various 
entries, after which the P. E.y and reliability of type A is com- 
puted for each. This reliability is obtained by dividing the average 
effect by its probable error (P. E.y,) and then looking up the re- 
liability in a table as indicated on p. 45. The third reliability (Type 
B) has a somewhat different meaning. Theoretically, it corres- 
ponds approximately to what would have been the reliability if 
there had been no variability among the various subjects in their 
reactions to the drug, but only a variability of each subject from 
his own central tendency from day to day.® This latter variability 
is expressed in the average of the column of P. E.’s, which, for the 


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THE INFLUENCE OF TOBACCO SMOKING 51 


first post-dosage test, is 1.62. This average is next divided by the 
square root of the number of entries (9) which is 3, on the prin- 
ciple that the probable error of an average (e.g. 6.42) is inversely 
proportional to the square root of the number of measures upon 
which it is based. This division yields .54 for the P. E.y4 of type B. 
From this a second reliability (Type B) is computed for the aver- 
age (6.42) in the usual way. The average of the absolute effects 
of the tobacco together with its reliability of type A are considered 
of most significance and accordingly are printed in more conspi- 
cuous type. The two remaining reliabilities are valuable chiefly as 
supplementary evidence. 

A glance at the body of Table VI shows that the habitual smok- 
ers, almost without exception, received a stimulation from the 
smoking. While the non-smokers are too few in number to base 
extensive generalizations upon, they show the same general ten- 
dency. If there is any difference between the two groups it is that 
the non-smokers have a somewhat greater immediate stimulation 
than the habitual smokers but recover from it somewhat more 
quickly. Two minutes after smoking, the habitual smokers show 
an average stimulation of 6.4 beats per minute. This falls to 5.76 
beats stimulation 37 minutes after smoking, to 3.59 beats 1 hour 
and 12 minutes after, but rather unexpectedly shows a slight in- 
crease in stimulation after 1 hour and 43 minutes. 

This apparent increase at the end of the experimental day is 
due in part to the fact that subject No. 10 had no entry on the last 
post-dosage test. This fact does not account for the gain, though, 
because a tendency in the same direction is apparent in Fig. 2 
where the missing data for this subject were supplied by inter- 
polation. The facts are brought out still more clearly by Fig. 3 

3 Another way of saying the same thing would be to say that the reliability 
of type A gives the probability of getting the same type of result if the experi- 
ment were repeated with new subjects chosen at random, whereas that of type 
(B) gives the probability if it were repeated with the same subjects. If this 
assumption were strictly true, the P. E.y4 of type B ought never to exceed the 
P. E.y of type A except as result of chance sampling, and should usually be 
less. This, while true in the tables under consideration, is by no means always 
the case. The rather general equality of the two types of P. E. would seem to 


indicate that the individual differences in the response to tobacco are not very 
great. 


52 CLARK Le HOLE 





Number of heart beats per minute in excess of normal 





(Normal) 0 
1 2 5 > 


Post-dosage test 


Fic. 3. The return of the heart rate to normal after smoking, habitual 
smokers. 


which shows the amounts of stimulation on each of the four post- 
dosage tests.* Here we can see the rate falling uniformly towards 
the normal throughout the post-dosage period except at the end of 
the experimental day. Here, instead of continuing to fall as one 
might naturally expect, we find an actual rise. This curve is based ° 
*It should be pointed out that the data upon which the curve of Fig. 2 is 
plotted included all the experimental days, whereas that of Table VI included 
all but the first day of each subject just as with the other tests. For this reason 


there are minor differences between the curves and the table. Fig. 3 is plotted 
from the same data as Fig. 2. 


THE INFLUENCE OF TOBACCO SMOKING 53 


upon averages from such a very large number of data that this 
interruption in the return to normal cannot be due to chance. The 
explanation seems to be that the group of subjects as a whole had 
a tendency to a mild excitement at the approach of the end of the 
somewhat arduous experimental day. Owing to the control meth- 
ods used, it is quite clear, of course, that for such an effect to be 
produced, the causal factor must operate more strongly on the 
tobacco days than on the control days. Indeed it is in this that its 
chief significance probably lies. 

It will be seen (Table VI) that the reliabilities of all the aver- 
ages and of both types are extremely high, which indicates that 
there is no question but that smoking stimulates the heart rate. In 
most cases the reliabilities are 1.000 or perfect. As a matter of 
fact perfect reliabilities are never obtained from such data. The 
1.000 was recorded in each case because the actual figures obtained 
by the computation were nearer to 1.000 than to .g99. 

Certain conclusions may be drawn from the above results: 

1. Tobacco smoking causes a fairly uniform stimulation of the 
heart rate. 

2. This stimulation, while disappearing fairly uniformly with 
the passage of time, is by no means gone an hour and 43 minutes 
after the termination of the smoking. 

3. Habituation to the use of tobacco seems to have little or no 
tendency to establish a tolerance with respect to heart rate. 

4. The heart rate appears to be more susceptible to the in- 
fluence of interest and excitement after smoking. 

The high degree of statistical reliability of the chief results 
summarized above, together with the fact that they agree in detail 
with the findings of both Payne and Dowling (see above p. 6 ff.) 
enable us to consider them as established. 


CHAPTER IV 


THE EFFECT OF SMOKING ON THE STEADINESS OF THE HAND 


In the present chapter, we pass from the automatic activity of 
the heart to a consideration of the involuntary muscular tremor 
of the arm and hand. It is assumed that steadiness is a desirable 
trait and that the steadier the hand the more efficient the voluntary 
muscular control. A certain amount of tremor is, of course, nor- 
mal. The question before us is: Does the smoking of a pipe of to- 
bacco increase or decrease this amount ? 

The method used in measuring the amount of tremor in the 
present experiment was adapted from Whipple.* The apparatus 
consists essentially of a stylus and a white metal plate which is 
pierced with two rows of holes of progressively varying size 
(Plate 4). The subject was seated comfortably in a swivel chair 
with the plate placed on the edge of the table before his right hand. 
The stylus was held like a pencil. The subject was directed to get 
in readiness and at the signal “‘Go”’ to place the stylus in the right- 
hand hole of the upper row and hold it there so far as possible 
without touching the plate, until told to stop. The arm was held 
well away from the body with the elbow bent at an angle of about 
110 degrees. The hole was 5.1 millimeters in diameter while the 
stylus was 3.1 millimeters in diameter. The time interval used was 
I minute and was measured by a stop-watch. The score was the 
number of contacts made by the stylus during the one-minute 
period. 7 

The number of contacts made was automatically recorded by an 
electric counter which was placed in circuit with the plate, stylus 
and several batteries, in such a way that when the stylus touched 
the plate a current passed through the counter and was instantly | 
registered. The hand of the counter was always placed on zero at 
the beginning of the test so that the score could be read off directly 
without computation at the end of the minute. Connected with the 
same electric circuit but shunted around the electric counter was 


‘ Whipple, G. M. Mental and Physical Tests, Simpler Processes, p. 155 ff. 


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THE INFLUENCE OF TOBACCO SMOKING 55 


an electric buzzer which sounded during each contact. The buzzer 
served to warn both subject and experimenter of any tendency to 
permanent contact. Both buzzer and counter, though on the same 
table, were placed behind a black screen partly to prevent distrac- 
tion of the subject’s attention but especially to prevent the subject 
from noting his score and thus setting up a possible vicious sug- 
gestion. For similar reasons the subjects were directed in their 
preliminary instructions, never to ask for their scores or indeed 
to think about them at all except to do their best on every test.” 

The detailed results of a typical habitual smoker (subject No. 
15) are shown in Table VII. The method of computing the effect 
of the tobacco is similar to that described above, pp. 39-45 and 
48-51. On the second test of the day (first post-dosage test) this 
subject shows a distinct gain in efficiency on the control days but 
a very marked loss in efficiency on the tobacco days. The imme- 
diate net effect of the tobacco on this subject is an increase in tre- 
mor of slightly more than 21 contacts per minute, over a normal 
of about 12. This amounts to an increase of over 182%. On the 
fourth test, however, at the conclusion of the experimental period 
and an hour and 23 minutes after the conclusion of the smoking, 
this has practically disappeared. It may also be noted that the 
statistical reliability of the results of all but this one period are 
very satisfactory. 

The final results of the investigation of the effects of smoking 
on steadiness are summarized in Tables VIII and IX for the non- 
smokers and the habitual smokers respectively. These tables are 
constructed and the various computations made exactly as in the 
corresponding tables given on pp. 49-50. An examination of these 
tables shows at once that the smoking has resulted, upon the whole, 
in a distinct increase in the tremor of both groups of subjects. 
This is particularly striking with the habitual smokers, where the 
increase in tremor on the first post-dosage test averages over 60%. 
About half of this increase has disappeared 48 minutes after the 
smoking, however, and only a trace is left I hour and 23 minutes 
after. 


2 These instructions were general and applied to all the tests alike. 


56 CUARR AL -AULE 


A graphic comparison of the average course of the tremors on 
the tobacco and on the control days is shown in Figures 4 and 5. 
In Fig. 5 the marked divergence of the two curves after the dose, 
shows the great increase in tremor of the habitual smokers im- 
mediately after the dose, while the drawing together of the curves 


TaBLe VII 


Tremor, subject No. 15, habitual smoker. Score, number of contacts sits 
made in hole during one minute, 


Difference between normal of day 














Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I IP eal y. II III IV Difference 
days: (Normal) 

Nov. 8 19 ig 10 ‘(i + 8 + 9 +12 + 9.66 
ae Oe 15 5 3 — 5 + 5 + 7 + 2.33 
oe Weta 6 SPE oO 0 fog tele oy ae area 
EEE Resa aye 12 3 6 0 + 9 + 6 + 5.00 
Wino as 18 age TK) — 5 + 10 + 3 + 2.66 
hol HT Rip 4 de eis Hie SE ery eee 
ae Le nes pers eet Mea eee CANT EIEN Oey 
ile yt uae 1 eebai ti bene | Soil Pee go ae Saag 

Total 084 69% 49 acho thai dp 49° D1gei 7 Sises 

Average 105 8.62 5.25 65 + 187 + 525 + 40 + 3.707 

MEEV Ore ee eee eee 4.13 3.75 4.5 2.97 

Pala cba ioe hat sents, 1.23 1:19 ented .887 

Tobacco 
days: 

Nov. 21 36 18 6 — 15 + 3 +15 + 1.00 
A 6 20 78) Ae — 14 — 17 — 6 -— 12.33 
ge gab jey Be) 62 35 19 — 43 — 16 0 — 19.66 
Lae co 53 28 39 — 28 — 3 —14 — 15.00 
Pala ale 43 31 5 — 30 — 18 + 8 — 13.33 
mee ity 12 36 8 4 — 24 + 4 + 8 — 4.00 
“420 5 10 12 2 — 5 — 7 + 3 — 3.00 
alone} 20 ail 3 — 10 — il + 7 — 1.33 
i ABS 6 13 24 2 — 7 — 18 + 4 — 7.00 

Total LET 2935 el SORE 2 —176 — 73 +25 — 74.66 

Average 13 32.55 21.1110.22 — 1955 — 8.11 — 2.77 — 8.295 

Mii Viacaswort Caetact Kaeo cane 10.39 8.12 6.30 6.03 

Pate Bia er ee ee ee 2.93 2.29 Lal? 1.70 

Effect of 

Tobacco: 

Diff erence 2.5.2 y ae Saco — 2142 — 1336 — 122 — 12.00 

Bs) Egy pettwwcernthe «nee ae See etn 3.18 2.55 2.22 1.92 

Ratio Wide des 0 wiGrelk yn as Baie w' Bard entre 6.74 5.24 5.49 6.25 

Reliability roe are ae oes .99997 .9998 .6447 .99997 


Pericent:gain-grneloss <.17 8-062 —182.29 —113.70 —10.88 —102.12 


THE INFLUENCE OF TOBACCO SMOKING 57 


Average number of tremor contacts per minute 


2 4 
Number of test 








Tobacco days —-—--—Control days 


Fic. 4. The effect of smoking on tremor of the hand, non-smokers. 


at the end of the period indicates the gradual recovery pointed out 
above. For some reason the average of the pre-dosage tests of the 
non-smokers on the tobacco days differs considerably from the 
corresponding average on the control days. This makes the de- 
tailed interpretation of the data from this particular set of sub- 
jects somewhat uncertain. From the data taken as a whole, how- 
ever, a number of facts stand out quite clearly. They may briefly 
be summarized as follows: 

I. The smoking of a pipe of tobacco produces a marked in- . 
crease in the tremor of the arm and hand. 

2. With the ordinary smoker, recovery is nearly complete an 
hour and 23 minutes after the termination of the smoking. 

3. Habituation seems, if anything, to have increased the sus- 
ceptibility of subjects to this particular action. 


58 CLARK L. HULL 


Average number of tremor contacts per minute 
~ 
° 





Number of test 





Tobacco days =-=Control days 


Fic. 5. The effect of smoking on tremor of the hand, habitual smokers. 


The above results harmonize well with the findings of previous 
investigators, in so far as comparable data have been reported. Such 
as are available have been described in some detail above (p. 7). 
If anything, the present results show a smaller increase in tremor 
as a result of smoking than has usually been found. Froeberg, 
whose results are probably the best in this respect, found an in- 
crease of 120% with non-smokers. Unfortunately, he does not 
state how many minutes after the termination of the smoking this 
particular test was made, though there are certain indications that 
it was given immediately. If this be true, the divergence may be 
attributed, in part at least, to the fact that this test in the present 
series came some 13 minutes after the smoking. During this period 
there must have been considerable decrease in the tremor if we 
may judge by what took place afterward (see curve, Fig. 5.) At 
all events, there is perfect agreement that smoking causes a marked 


59 


THE INFLUENCE OF TOBACCO SMOKING 

















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XI ATV EL 


THE INFLUENCE OF TOBACCO SMOKING 61 


increase in tremor of the hand. This may be considered as estab- 
lished. The present results indicate in addition that this is as great 
for habitual smokers as for non-smokers and that for the ordinary 
smoker, recovery is practically complete an hour and 23 minutes 
after he has ceased smoking. 


CHAPTER V 


Tue EFFECT OF SMOKING ON THE RATE OF VOLUNTARY 
MovEMENT 


In the present chapter we pass from the consideration of auto- 
matic or involuntary movement to that of the rate of voluntary 
movement. The method of measurement chosen was the tapping 
test adapted from Whipple.* The tapping board and stylus were 
tried on some preliminary subjects but is was found unsatisfactory 
because the stylus frequently became oxidized on the end so that 
registration was faulty. The instrument finally adopted was a 
Stoelting round-base telegraph key with the spring set to that it 
required a pressure of about 500 grams on the button to produce 
a contact. This key was placed in circuit with four dry cells and 
the electric counter mentioned above (Chapter IV). As in the 
steadiness test, the counter was placed behind a small black screen 
so as to be out of the subject’s view. He sat in a swivel chair with 
his side to the table upon which the key was placed, in such a way 
that his forearm could rest on the edge of the table if desired. He 
was directed to tap 400 times as quickly as possible and to go at 
his maximum speed from the very beginning. Time was taken 
with a split-second stop-watch, one hand on the watch being stop- 
ped when the counter registered 200 taps and the other when it 
registered 400 taps. In the present chapter we shall consider only 
the time required for the 400 taps. 

A typical set of results in this test is shown in Table X. The 
construction of the table and the methods of computation are the 
same as described above, pp. 39 ff. and 49 ff. The final averages 
with this subject shows a slight loss in speed after smoking but 
the statistical reliabilities are so low that, with the possible excep- 
tion of test III, they have no significance. On this one test the 
chances are about 19 to 1 that a loss in speed has really resulted 
from the smoking. 


1 Whipple, G. M. Mental and Physical Tests, Simpler Processes, p. 130 ff. 


THE INFLUENCE OF TOBACCO SMOKING 63 


The final results of the investigation of the effect of smoking 
on rate of tapping are summarized in Tables XI and XII for the 
non-smokers and the habitual smokers respectively. The minus 
signs, as usual, mean a loss in efficiency—in this case a retardation 
in the rate of tapping. A glance at the signs in the body of these 


TABLE X 


Tapping, subject No. 15, habitual smoker. Score, number of seconds required 
to make 400 taps with a telegraph key. 


Difference between normal of day 


Original scores and subsequent tests 


















































Test Test Test Test Test Test Test Average 

Control iI II phy ea at II III IV Difference 
days: (Normal) 

Deve aS poiat0.G 46 Fam Teen TDG 8.4) Pa 8 9 886 
ie. 0 2.00 92 70.6915 69 69.8 +2.0 +3.6 +2.8 +2.80 
He soa ly 73.2 68.4 70.2 73.4 +4.8 +3.0 — .2 +2.53 
eel TOPPA he? —1.2 +1.0 0. — .06 
516 68.6 66.4 66.0 68.8 +2.2 +2.6 — .2 +1.53 
e818 67.4 65.6 65.2 63.8 +1.8 +2.2 +3.6 +2.53 
419 64.4 64. 66.0 65.6 + .4 —1.6 —1.2 — .80 
“22 65.2 65.2 64.8 65.8 0.0 + .4 — .6 — .06 
Total 554.2 547.6 544.4 552.0 eG Gime SPOS eh 8. 8r ib at 
Average 69.27 68.45 68.05 69.0 + 82 +122 4 27 4+ 77 
SV Misraatan erates eee Scares ae ae es 1.875 1.625 1.46 1.571 
DES irre ode ohas ns 224 yale nie 5604 .4858 4364 .4695 
Tobacco 
days: 

Nov. 7 73.4 75.0 74.2 %6.2 —1.6 — 8 —2.8 —1.73 
Ce t9 712.2 72.2 69.2 69.0 0 +3.0 +3.2 +2.06 
os cub Ie 67.2 69.6 71.4 69.6 —2.4 —4.2 —2.4 —3.00 
a | 64.6 67.8 67.4 66.4 —3.2 —2.8 —1.8 —2.60 
NS 66.2 66.4 67.2 64.4 — .2 —1.0 +1.8 + .20 
ein ily 62.8 66.2 63.2 64.6 —3.4 — 4 —1.8 —1.86 
ont20 65.2 63.4 63.6 61.2 +1.8 +1.6 +4.0 +2.46 
Sipe L 61.4 61.4 62.6 64.6 0 —1.2 —3.2 —1.46 
eas 67.8. 63.4 > 66.4. 63.2 4a PL Ay Reh G ar 29-46 
Total 600.8 605.4 605.2 599.2 —4.6 —4.4 +-1.6 —2.47 

Average 66.75 67.26 67.24 66.57 — 61 — 49 + 18 — 27 
ee Re ae ee 1.901 1.679 2.864 2.062 
RE Me rd ails «oid Sie cre dain kde .5356 473 .807 581 
Effect of 
Tobacco: 

MI ELONCE tos + cass coe ve kets sss —133 —1.71 — 09 —1.04 
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Eetscentiegin or. loss! feces oe eG —195 —251 — 18 —1.58 


CLARK LOHULL 





























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IX FMV] 


THE INFLUENCE OF TOBACCO SMOKING 65 


tables shows at once that there is little tendency to any definite 
type of effect. About as many subjects show a gain in efficiency 
as a loss. The final average of the first post-dosage test with the 
non-smokers shows a gain in speed of about .8 of a second or 
about 1.5% whereas the corresponding average for the habitual 
smokers shows a loss of about the same amount. The reliability 
of type A in each case is low—approximately 9 to 1—which is the 
lowest ever used in scientific investigations and below the stand- 
ard adopted in the present monograph unless supported by other 
evidence. The reliabilities of type B, on the other hand, are quite 
satisfactory. This would seem to indicate that there are consider- 
able differences in the reaction of different people to the drug in 
the processes measured by this test. This view is supported by the 
considerable number of reliabilities of individual subjects which 
run up to .goo and above. 

‘The course of the tapping rate throughout the experimental peri- 
od, was computed and plotted as was done with the corresponding 
data on the steadiness test. As nothing of significance was re- 
vealed, the curves are not reproduced. This computation showed 
that the habitual smokers, on the average, tapped somewhat slow- 
er throughout the experimental period than the non-smokers, the 
groups requiring 63.3 seconds and 61.9 seconds, respectively. The 
difference of 1.4 seconds was at first taken to indicate a char- 
acteristic difference between the tapping ability of the two groups, 
but a computation showed that its reliability was only .750. This 
means that a difference as great as this might happen one time in 
four by mere chance and that it is not significant. 

The previous investigations of the influence of smoking on the 
rate of tapping have been reviewed above (pp. 8-9). They agree 
with the present results in showing marked individual differences 
among the various subjects in the nature of their reaction to the 
drug. The present writer has found no experimental evidence 
bearing on the influence of smoking on the habitual smokers, un- 
less Johnson’s subjects were of that type. If they were, his results, 
so far as they go, agree with those of the present investigation in 
showing a slight loss in efficiency. Froeberg’s results, which alone 
in this field are sufficiently numerous to be worthy of serious con- 


CLARK LY AVULLE 








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TIX TMV 


THE INFLUENCE OF TOBACCO SMOKING 67 


sideration, show an average gain of 1.6% with non-smokers. This 
is in almost exact agreement with the corresponding results with 
our own non-smokers. This obviously strengthens considerably 
the somewhat meagre statistical reliability of our own results with 
this class of subjects. We may conclude then, that some 30 minutes 
after smoking, there is a fair probability that non-smokers as a 
group show a slight stimulation in rate of tapping. The evidence 
is somewhat weaker that habitual smokers show an equally slight 
loss in speed of tapping. The effect, if any, of habituation, is thus 
to reverse the effect of the drug. At the end of an hour all trace 
of either effect is quite lost. Lastly, all available results alike show 
striking disagreements among the various subjects as to the nature 
of the individual effects of tobacco smoking as measured by this 
test. 


CHAPTER VI 


THE EFFECT OF SMOKING ON MUSCULAR FATIGUE 


In the last chapter it was pointed out that the time required for 
the subject to make the first 200 taps was recorded along with that 
for the 400. This was done for the purpose of securing a measure 
of muscular fatigue. If a subject starts tapping at his maximum 
speed, he will ordinarily require longer for his second 200 taps 
than for his first 200. Accordingly, if we multiply the time re- 
quired for the first 200 by 2 and subtract the results from the time 
required by the 400, the difference will be the length of time that 
the second 200 taps required over that consumed by the first. This 
difference, then, becomes a convenient measure of the amount of 
fatigue produced by the activity in question. While doubtless not 
yielding results exactly comparable with those obtained by the 
ergograph, the method does yield a measure of a certain kind of 
fatigue of rapid onset, and has the distinct advantage or requiring 
no additional effort or time from either the subject or the experi- 
menter. Indeed, if it had been necessary to introduce a special test 
for the purpose, no data on muscular fatigue could have been se- 
cured at all. 

The fatigue results of the typical subject are shown in detail in 
Table XIII. The construction of this table and the various compu- 
tations are similar to the corresponding ones in previous chapters. 
It will be seen that this subject shows a distinctly better resistance 
to fatigue after smoking than after the control dose. 

The results of the entire investigation of the effect of smoking 
on muscular fatigue are shown in Tables XIV and XV for the 
non-smokers and the habitual smokers, respectively. It will be noted 
that the results of one subject in each group are lacking because: 
of the inadequacy of the stop-watch used on those occasions. The 
final averages of these tables are supplemented by the curves of 
Figs. 6 and 7. These show for the respective groups of subjects 
the average course of the fatigue throughout the experimental 
period for the control days and the tobacco days in parallel. 


THE INFLUENCE OF TOBACCO SMOKING 69 


The most striking effect of smoking revealed by this set of data 
is the greatly strengthened resistance to fatigue among the non- 
smokers. On the first post-dosage test, there isn’t a single negative 
sign among these subjects and the statistical reliability indicates 


TABLE XIII 


Muscular fatigue, subject No. 15, habitual smoker. Score, number of seconds 
required to make the second 200 taps in excess of the number required for the 
first 200 taps. 


Difference between normal of day 




















Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I Liste TV II III IV Difference 
days: (Normal) 

Nov. 8 42° 2.4 4.0 6 + 1.8 + .2 + 3.6 + 1.86 
sa 10 1 SecA 2 en 4 Ped 8 — 2.4 — 1.6 0 — 1.33 
waray 6.4 36.2) (3.4018 iS Pa SO ees A a Ek 208 
Selo 3.00 mo. No.O%ee ace 0 — 6 + .8 + .06 
“ 16 ep Meee wosege | SOP Beene ty Oa Me Be athe WO ET 
dike: 10 40 28 # «2.6 — 3.0 — 1.8 — 1.6 — 2.13 
4 ey I Ae 1AGemuao — 2.0 0 — 1.2 — 1.06 
oe 2 ee a Omens + 8 0 — 1.8 — .33 

Total 21.8 25.2 23.2 16.0 — 3.4 — 14 + 5.8 + 33 

Average PIP). BRS BANE pt — 42 — 17 + 272 + 04 

INIT OMcts oe rei crte caroeea Susiels oe 1.53 .98 1.88 1.25 

Vi SD Se ee ee 46 29 56 37 

Tobacco 
days: 

Nov. 7 stroke Soke 1.0 — 1.2 0 + 1.2 0 
ee 9 , DiOie. 2a. Oe Ls + 2.8 + 2.0 + 3.2 + 2.66 
waele eee 2 Oe: 4 + 4.8 + 1.4 + 2.4 + 1.53 
oid Sgt so 26 8.8 16 + 1.6 0 aN ck 9 fe 
les A Ae Ose 8 8 + 1.0 + 3.4 + 3.4 + 2.60 
commen Seo OV) 32100 5 2:6 + 2.2 + 1.2 + 6 + 1.33 
sce () OMT SA PA 8 SPA — 2 0 0 — .06 
“« 91 se S48) 3.8 2.2 cay i Telnet) oe eae, a i) eh ms 
a 98 Oa 46°. 28 8.2 Sl Seen cote G pt tom Sih nee ets 

Total etm 24 2 ell, oat Lo.6 + 7.0 + 9.4 +15.6 +10.65 

Average 3.46 2.68 2.42 1.73 + 78 +104 + 173 + 118 

yh) Was og cit 4s Rea 1.10 .85 1.10 83 

DE ares I Rass 31 24 31 23 

Effect of 

Tobacco: 

ID ferencea on casi ae auaacerae.s +120 +121 +101 +4114 

Leal) Seagate Ags nee 55 38 64 44 

ATTEN ool we winiee sie eeitiele cicecele 2.18 3.18 1.58 2.59 

LC SALSS Fa GN SR eh 927 983 .859 


.96 
her cent gam or loss ....6. 63... 4-88.83 +89.15 +382.68 +36.99 


70 CLARK L. HULL 


Number of seconds decrease in tapping speed resulting from fatigue 





Number of test 





Tobacco days —-—-—Control days 


Fic. 6. The effect of smoking on muscular fatigue resulting from tapping 
with a telegraph key, non-smokers. 


that there is less than one chance in a hundred that it does not in- 
dicate a real difference in favor of the tobacco days. The curves of 
Fig. 6 confirm this by their marked divergence following the dose. 
By the end of the experimental period, however, the curves have 
nearly come together again, showing that after an hour and 40 
minutes the special resistance has practically disappeared. 

In the case of the habitual smokers, there appears also to be an 
increased resistance to fatigue after smoking, though it is distinct- 
ly less in amount and probably disappears somewhat more quickly 


THE INFLUENCE OF TOBACCO SMOKING 71 


Number of seconds decrease in tapping speed resulting from fatizus 





Number of tost 





Tobacco days -—-—-Control days 


Fic. 7. The effect of smoking on muscular fatigue resulting from tapping 
with a telegraph key, habitual smokers. 


than with the non-smokers. The statistical reliability of the differ- 
ence in this case is clearly below the standard adopted in the present 
investigation but it is so strongly supported by other considera- 
tions that it may be accepted with a fair amount of confidence. In 
the first place, the curves of Fig. 7 show about twice as great a 
separation as the averages from the corresponding table would lead 
one to expect. The reason for this apparent discrepancy between 
the table and the curves lies in the separation of the two curves at 


CLARK OL HULL 


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THE INFLUENCE OF TOBACCO SMOKING 


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74 CEARKS LO AULL 


their point of origin, whereas theoretically (i.e., except from chance 
sampling errors) they should start from the same point. The above 
view also finds support in the characteristic subsequent course of 
the curves as well as in the general probability of a reduction in 
effect of a drug resulting from habituation. 

It will also be noted in Figures 6 and 7 that the habitual smok- 
ers show throughout, a smaller amount of fatigue than the non- 
smokers. On the normal performances preceding the dose, the non- 
smokers show on the average nearly .7 of a second more fatigue 
than the habitual smokers, which amounts to over 21 per cent. The 
statistical reliability of this result is .852, which indicates that the 
chances are about 6 to 1 that there probably is a real difference be- 
tween the two groups in favor of the habitual smokers. It is true 
that this reliability unsupported by other considerations is not 
sufficient to base action upon but as we shall encounter similar 
differences from time to time throughout the present study, a 
number of possible explanations may profitably be considered at 
this time. It is conceivable, for example, that in the case of the 
habitual smokers the immunizing effect of the last smoke of the 
day preceding the experiment may have lingered long enough to 
make them less susceptible to fatigue than the non-smokers. But 
this hypothesis is at once negatived by the fact that the immunity 
which results from the smoking during the experiment itself is 
lost within a couple of hours after smoking, whereas these subjects 
had not smoked for 3 hours or more preceding the test in question. 
A second possibility it that the continued use of tobacco may have 
produced a lasting tendency to immunity in the habitual smokers, 
making them more or less permanently superior to non-smokers in 
this respect. The writer inclines, however, to explain the difference 
on the assumption that the smokers were a selected group. They 
appear to have been somewhat more easy-going as a group than 
the non-smokers and possibly did not put quite so much effort into 
the tapping. In this connection it may be recalled that the habitual 
smokers tapped, on the average, slightly slower than the non-smok- 
ers. This would naturally produce less fatigue. The selective factor 
referred to was the choice of subjects for this group who were, so 
far as possible, exclusively pipe smokers but from a population 
composed almost entirely of cigarette smokers. 


THE INFLUENCE OF TOBACCO SMOKING 75 


We may now summarize the results of the investigation as fol- 
lows: 

I. Non-smokers show unmistakably greater resistance to fa- 
tigue in tapping as a result of smoking. 

2. This immunity to fatigue is gradually lost so that 1 hour 
and 40 minutes after smoking, only a trace remains. 

3. Habitual smokers as a group also show an increase in re- 
sistance to fatigue after smoking, though it is less in amount and 
disappears more quickly than with the non-smokers. 

4. Habituation thus appears to produce a partial tolerance to 
this action of tobacco. 

5. -On the normal tests preceding the dose, the habitual smok- 
ers as a group show less fatigue than the non-smokers. This is 
‘ thought to be due in some way to the factor of selection. 

The evidence from previous investigations as to the effects of 
smoking on muscular fatigue with human subjects, has been sum- 
marized above, pp. 9-11. The bearing of these experiments on the 
results of the present investigation are somewhat uncertain owing 
to differences in technique. The investigations in question have 
used one form or another of the ergograph. This yields a score 
primarily in terms of the strength of muscular contraction at 
constant rate, whereas the score in the present investigation is in 
terms of the rate of contractions at constant strength with the 
latter well below the fatigue level. Moreover, the fact that the in- 
vestigations in question are based on such a small number of data 
introduces additional complications. All 4 studies taken together 
employ a total of only 5 subjects. Lastly there is little agreement 
among these studies as to results obtained. One of them shows a 
definite loss in efficiency, two show no reliable effect and one shows 
a fairly definite advantage. Of the 4 investigations the technique 
of Hough differs least from that used here. He employed a spring 
ergograph and took as a measure of fatigue the rapidity of the fall 
of the work curve which is substantially the present method of 
scoring. He found exactly as in the present study, that smoking 
enabled him to resist the onset of fatigue considerably better than 
when he did not smoke. 

Hough states in discussing the bearing of his results on muscular 


76 CLARK, EL HULL 


fatigue in general, that certain individuals at least, are enabled to 
bear fatiguing work more easily by the use of tobacco.* 

In the light of all the available evidence, then, we may say that the 
present results indicate pretty definitely that the early part of one 
type of work curve falls off less rapidly after smoking than when 
the subject has not smoked. The present investigation tells us noth- 
ing positively about the subsequent course of the curve though 
there is some presumption that it follows the same tendency. There 
is some corroborative experimental evidence from a single subject 
(Hough) in support of this view, as well as a certain popular be- 
liefs. There is, on the other hand, some experimental evidence 
from a single subject (Lombard) which conflicts with it. It is 
therefore unsafe to draw any positive conclusions at this time as 
to the influence of tobacco on the onset of fatigue for muscular 
work in general. In view of the inadequate and conflicting nature 
of the ergographic results reported thus far, the present investiga- 
tion serves at least to call seriously in question the statements 
prevalent in the propagandist literature, that tobacco greatly re- 
duces resistance to fatigue. The matter needs a careful and thor- 
ough investigation at the hands of trained physiologists. — 


1 In this connection we may also recall rumors current during the late war to 
the effect that soldiers under the necessity of exerting themselves to the maxi- 
mum for protracted periods, were enabled to a large extent to resist the normal 
onset of fatigue by the smoking of cigarettes. This may have been propaganda, 
however. 


RiP PT ER Vil 


THE EFFECT OF SMOKING ON THE RATE OF CANCELLING A’S 


In the present chapter we pass from the processes mainly physi- 
ological to those in which the emphasis is primarily psychological. 
The A-test presents on the psychological level a measure of visual 
acuity and discrimination, combined on the physiological level 
with a measure of the rapidity of relatively simple movements of 
the hand. The test thus involves the elements of much of the re- 
petitive work of the modern factory and the results have a little 
special interest because of this. The printed material for this part 
of the investigation became available only after the first 7 of the 
non-smokers had been tested so that the results to be reported ap- 
ply primarily to the habitual smokers in whom, fortunately, our 
interest mainly centers. 

The form of the A-test employed is reproduced in Appendix K, 
and contains 100 A’s. It is an adaptation of a form in wide use.* 
Fight different forms of this test were specially printed but with 
no external evidence to distinguish any of them from the rest. In 
order to make all eight forms equal in difficulty they were made up 
in such a way that each line of each of the eight forms had the same 
number of the various letters in it as the corresponding lines of 
the other forms, only the different lines were arranged differently 
in each form according to chance drawings. Likewise the order of 
the letters in the respective lines were differently arranged in the 
different forms according to chance. The trouble and expense of 
preparing and printing so many forms of this test were undertaken 
in order, so far as possible, to prevent the subjects from gradually 
learning the positions of the A’s on the test blank. If this had taken 
place, the test would gradually have lost its discriminatory nature 
and have degenerated into something like a test of the rate of 
voluntary movement. As a further precaution in the same direc- 
tion, no intimation was given the subjects that the same form of 


1 Whipple, G. M. Mental and Physical Tests. Simpler Processes, p. 307. 


78 CLARKS LHGLE 


the test was ever repeated, though as a matter of fact each form 
always was repeated 9 times during the 18 days. That the method 
succeeded is indicated by the fact that introspections taken from 
a number of subjects at the end of their last day in the experiment 


TABLE XVI 


Cancellation, subject No. 15, habitual smoker. Score, number of A’s cancelled 
in one minute plus half the A’s for which a mark was made but failed to touch 
the letter. 


Difference between normal of day 


Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 
Control I II LT isl II III IV Difference 


days: (Normal) 












































Nov. 8 69 76 76.5 68.5 +70 +75 — 56 + 4.66 
Fhe Pah Tit 72 hy it — §.0. + 1.0 0 — 1.33 
pie Sh 78.5 69 72.5 16 —95 —60 —2:5 — 6.00 
ale di re bliy: a Y4s3 (90m +65 +75 +65 + 6.83 
nlG 75.5 76 kaye ARs + 56 +10 —40 ‘— .83 
Se a: 69/0 12-00 60.00 LG +35 4110 +70 + 7.16 
ay 9 Tippee Sirona 4 oe 1 6: +40 —30 —15 — .16 
Ty, 79.5 81 DOU oTS +15 —40 —70 — 3.16 

Total 597.5 606 612.5 595.5 +85 +150 —2.0 + 7.16 

Average 74.69 75.75 76.56 74.43 + 106 + 187 — 25 + .895 

Mien. Wen pea oot eet bai aa es ae hee er 4.30 5.09 3.56 3.990 

PLS TS yey tc oan enone OR ately at 1.28 1.52 1.06 1.190 

Tobacco 
days: 

Nov. 7 68.5 68.5 64 70 0 —45 +15 — 1.00 
“ 9 75 73 74.5 73.5 —20 —056 —15 —1.33 
SAP 1 78 79 83 83 +10 +50 +50 + 38.66 
WL 79 79 (hy YB 0. —25 —60 — 2.83 
ie a Ws 76:5) 19.560) a2 (03 +30 +55 —35 + 1.66 
Stes 17, 71.0 80 81 79 + 90 +100 +80 + 9.00 
LGPL, 81.5 69 80 83 —125 —15 +15 — 4.16 
Stott 87 83:5 79 78.5 —35 —80 —85 — 6.66 
eas 82 77 (3.0m lec —50 —85 —85 — 7.33 

Total 698.5 688.5 693.5 686.5 —10.0 —6.0 —12.0 ._— 9.00 

Average 77.61 “76.5 “77.05 76.28  —— Ll” — bbs — 133) 100 

Mie Vit Pe ee ie Sc ee ae eae Set eee 4.12 4.94 4.74 3.85 

PEA ee lest se eats a crass ile ete 1.16 1.39 1.34 1.08 

Effect of 

Tobacco: 

Difleretice e+ cs neice ee ane — 2.17 — 242 — 108 — 1.895 

Pi, Bary ov es as eatcte ciota Ose ceo eee eres a 5 Rey 2.06 nye 1.61 

Ratio vie ick cre Sa a oe tebe ee 1.25 ue .63 1.18 

Reliability) craw mie ance aha Perens sate eei .8004 Weck .6571 781 


Per cent. gain "orilosst. 07 as tse 5 te a — 285 — 3.18 — 142 — 2.49 


THE INFLUENCE OF TOBACCO SMOKING 79 


revealed no case where a man had even noticed the second appear- 
ance of any form of the test. 

In order to eliminate any constant errors due even to an un- 
conscious tendency to learn the positions of the A’s, the various 
forms were given in a constantly but systematically varying order 
yet one such that on any given experimental day all four forms used 
had previously received the same amount of practice. There was, 
of course, a great deal of improvement in speed of cancellation 
from ordinary practice effects, but this was a factor not likely to 
introduce any important change into the nature of the test such 
as learning the positions of the A’s would have done. Constant 
errors due to practice effects were automatically eliminated by 
features of the technique previously discussed (p. 38). 

The form of giving the test was as follows: 

The subject was given a special blue pencil and a test blank was 
placed face down on the table before him. He was instructed that 
at the signal ‘“Go”’ he was to turn over the sheet and cancel out the 
A’s as rapidly and accurately as possible until told to stop. One 
minute was ordinarily allowed. On the latter days of the tests, some 
subjects became so rapid that there was danger that they might fin- 
ish before the expiration of the allotted time. In such cases the time 
limit was reduced to 50 seconds, the time being constant through- 
out any given experimental day. As an added precaution, the re- 
duction of the time was made at such a point in the experiment 
that there would be an equal number of control and tobacco days 
affected by it, though the methods of computation and control 
probably made this unnecessary. The score was the number of A’s 
cancelled plus half of the A’s for which a mark was made but 
failed to touch the letter. In this score no deductions were made 
for errors. These will be considered separately in the next chapter. 
A special set of 8 celluloid stencils for scoring the various forms 
was made by stamping out squares over each A on a given blank. 
These aided greatly in the speed and accuracy of the scoring, par- 
ticularly in the case of the errors. 

The cancellation results of the typical subject appear in Table 
XVI. The construction of this table and the various computations 
are exactly as described above, pp. 39 ff. and 49 ff. This subiect 


CLARK L. HULL 


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81 


THE INFLUENCE OF TOBACCO SMOKING 























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82 CLARKSLSAUELE 


shows a slight loss in speed of cancellation after smoking, but the 
reliability of the difference is so low that, standing by itself, it has 
no significance. 

The final results of the two non-smokers are shown in Table 
XVII and of the habitual smokers in Table XVIII. In addition, 
the average course of the rate of cancellation throughout the ex-- 
perimental day was computed for the smokers for both control and 
tobacco days and plotted in parallel. Nothing of importance was 
revealed, however, and as the differences involved were too minute 
to show well on a graph of ordinary size, they are not reproduced. 

The results of the non-smokers are too few to be of much sig- 
nificance, though, so far as they go, they suggest a slight loss in 
efficiency as a result of smoking. The habitual smokers show little 
agreement among themselves as to the nature of the effect and none 
of them shows a satisfactory individual reliability. Turning to the 
averages of the entire group we find that on the first post-dosage 
test (16 min.) there is practically a zero effect. At 51 minutes there 
appears a minute loss of about 1 per cent and at 1 hour and 26 
minutes, this loss shows a slight increase. Small as it is, the effect 
in the last case mentioned has a statistical reliability reaching the 
lower limits adopted in the present investigation as satisfactory. 
This would seem to indicate that, within the limits covered by the 
present investigation, tobacco has a very slight inhibiting action 
on the speed of cancellation. It may or may not be significant that 
the loss in efficiency increases continuously throughout the post- 
dosage period. So far as the non-smokers go, they also suggest a 
similar tendency. 

The final discussion and evaluation of the above results will be 
deferred until the end of the following chapter. _ 


CHAPTER VIII 


THE EFFECT OF SMOKING ON THE ACCURACY OF CANCELLING A’S 


The technique of the A-test has been described in detail in Chap- 
ter VII. In addition to the score of correct cancellations secured 
from each test record, there was also obtained a score of errors. 
These errors were of three kinds: (1) the A’s overlooked, (2) the 
number of other letters incorrectly cancelled, and (3) the A’s 
where a stroke of the pencil was made with the evident intention 
of cancellation but where the mark failed to touch any part of the 
A. Each of these last was arbitrarily scored as % an error. The 
major part of the errors was of type (1). Despite their different 
nature, all three types of error were massed together without dis- 
tinction in the tables because the number of errors of any one type 
would have been too small for profitable statistical treatment. In- 
deed, with some subjects this was almost the case where all three 
were combined. The average score of all errors combined for the 
smoker subjects on the normal tests preceding the dose, was less 
than 2 per minute. 

The complete results from the typical subject on errors in can- 
cellation are shown in Table XIX. The construction of the table 
and the various computations are exactly as described above, pp. 
39 ff. This subject shows a tendency to an increase in accuracy as 
the result of smoking throughout the period. On the first post- 
dosage test the effect becomes large enough to obtain a satisfactory 
statistical reliability. 

The final results of the two non-smokers appear in Table XX 
and those for the habitual smokers are shown in Table XXI. As 
in chapter VII, the data from the non-smokers are too few to be 
of more than suggestive value. So far as this evidence goes, it 
points to a loss in accuracy as the result of smoking. The habitual 
smokers show a great lack of agreement among themselves as to 
the nature of the effect produced just as in the chapter on the rate 
of cancellation. The final averages of all the subjects in this case, 


84 CLARK L. HULL 


however, show a slight gain in efficiency as the result of smoking 
instead of a loss, though in no case does the amount of gain quite 
reach the level of statistical reliability adopted in the present in- 
vestigation as satisfactory. On the second and third post-dosage 


TaBLe XIX 


Errors in cancellation, subject No. 15, habitual smoker. Score, number of A’s 
omitted plus the number of other letters cancelled plus half 
the strokes which failed to reach the mark. 


Difference between normal of day 


Original score and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I II TET EV II III IV Difference 
days: (Normal) 

Nov. 8 BG AT yg 2s ey, 8 2 + 1.00 
SLO 4 4 2 2 0 +2 + 2 + 1.33 
rion ti) 3 2 2 3 +1 +1 0 + .66 
nS 2 2 3 4 0 —l1 — 2 — 1.00 
Come 2 ooo 3 —l1 0 +1 — .66 
eon18 S. SRS At tse ee bea7 0 ae “E7566 
este RY) 4 6 1 2 — 2 +3 + 2 + 1.00 
too, 2 2 5 5 0 —3 — 3 — 2.00 

Total 5 28 0 4 — 3 +5 +1 + 1.00 

Average S.1 2043.68 52.6 23.0 — 37 + 62 + 12 + .125 

IMIS Bae ctctacente toe ee oe oie ete .968 1.63 1.63 1.000 

Pye see acdc ciate sta Sabie’ .289 487 487 .299 

Tobacco 
days: 

Nov. 7 Bh ainGiaaSs id ad. +2 4.9 + 1.00 
a 8 0 6 1 + 8 +2 +7 + 5.66 
“ 192 Bogota ee ues ce “peg Wig s8 
en. 0 2 3 2 — 2 —3 — 2 — 2.33 
PAG are ares ees, Pat +4 are + 2.33 
a1 17 SAE 0b .cO aes ues. +3 bd + 2.33 
wr 20 al 2 1 0 —i1 0 +1 0 
Svnnro 5 2 2 8 + 3 +3 —83 + 1.00 
E28 2 2 6 7 0 et — 5 — 3.00 

Total 34 20 26 28 +14 +8 + 6 + 9.33 

Average ayer! 2 POPE LOWE. Palak +155 + 88 + 66 + 1.04 

MV Se teers lett girl cote oie RIO eae 2.39 2.15 2.67 1.89 

by TEE prey re ne ee en Brie fae .673 .606 152 532 

Effect of 

Tobacco: 

Difféfences isa Fein he eeu chew 192 4+ 26 + 54 + 91 

PL Erp pi oiosa.s os tiad'g alte wig atanene ate 3735 78 .89 61 

Ratio Sircccks cutee cc ieeresteraete tors 2.610 34 61 1.50 

Reliability: 32 20 te aan tel cokies oe 961 593 657 844 


Per cent gain or loss ..........++- 455.65 +7.58 +15.65° +2687 


85 


THE INFLUENCE OF TOBACCO SMOKING 











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IXX FHV 


THE INFLUENCE OF TOBACCO SMOKING 87 


tests with this group, the chances are about 15 to 1 that smoking 
really increases the accuracy of cancellation. It may also be signifi- 
cant that this average gain in accuracy increases from test to test 
very much as the speed of cancellation decreased from test to test 
with the same subjects. It should be noted in addition that this gain 
in accuracy is almost the same in amount as the loss in speed. 

The only investigation of the effect of smoking on cancellation 
found by the present writer is that of Bush. This study has been 
reviewed in some detail above (p. 11 ff.). Bush reports an average 
loss in speed of 17 per cent with a squad of subjects composed 
mostly of habitual smokers. He gives no results as to accuracy. 
The difference between the 17 per cent loss found by Bush and 
the 1 per cent or less found in the present investigation is really 
enormous and demands serious consideration. There are a number 
of differences in technique which might have contributed to this 
difference. Bush’s material was unspaced prose as distinguished 
from the random letters used by the writer. Of more importance, 
his tests before smoking were on E’s and after smoking were on 
A’s, the assumption evidently being that the two letters were equal- 
ly easy to cancel. Moreover, his subjects smoked only about half as 
long as those in the present experiment. He neglects to state how 
long after the smoking this test was given, but there is some in- 
dication that it was given immediately, whereas the present test 
was given 16 minutes after. In this connection it may be recalled 
that what little loss in speed is found in the present investigation 
appears only after an hour or more. The present writer inclines to 
attribute the difference found more to certain defects in Bush’s 
general technique such as the lack of a suitable control which have 
been pointed out by Froeberg and reviewed above, p. 12 ff. 

Ultimately, an issue of this kind must be decided by further and 
more careful experimentation. Meanwhile, so far as the present 
investigation goes, it indicates either that tobacco has no measur- 
able effect whatever on the cancellation of habitual smokers, or if 
it has any effect, it makes them a trifle more careful in their work 
which increases their accuracy slightly but at the sacrifice of an 
equally slight loss in speed. 


CHAPTER IX 


THE EFFECT OF SMOKING ON THE SPEED OF ORAL-READING 
oF IsoLATED WorpDs 


The next process to be investigated in our advance from the 
lower to the higher mental processes, is the effect of smoking on 
the rapidity of the functioning of thoroughly formed sensory- 
motor associative bonds of long standing. Few associations are 
more firmly established than that between the visual stimulus and 
the speech reaction in reading. Accordingly 30 common four-letter 
unrelated words were selected to be read orally. one at a time. The 
words were: wood, loaf, zinc, heel, shop, home, back, drug, wolf, 
kite, horn, gold, hand, hole, fish, cape, park, coat, cake, bear, lamp, 
boat, cool, frog, page, bird, song, bead, girl, duck. 

They were carefully typed on stiff paper which was later cut up 
in such a way that each word was in the middle of a card about an 
inch square. These cards were then attached in a chance order to a 
specially prepared canvas band, each by a drop of glue. The band 
was then suspended from the drum of an automatic exposure ap- 
paratus of special design.* In this way the words were exposed one 
at a time at a window in the front of the apparatus for a peri- 
od of five seconds (Plate 5). The shift from one word to the next 
was practically instantaneous, though during the exposure, the 
word was stationary. The subject was directed to Speak each word 
as quickly as possible after it appeared. 

The reaction-time was measured by a John Hopkins chrono- 
scope controlled by a tuning fork of special construction. The rate 
of this fork was calibrated against a Jaquet chronograph. It was 
such that the units of the chronoscope readings were .0034 of a 
second or approximately 1/300th. The chronoscope was connected 
electrically with the exposure apparatus in such a way that the 


1 For an account of this apparatus see Hull, C. L., Quantitative Aspects of 
the Evolution of Concepts, pp. 11-12 and 72. This study appears as No. 123 of 
the Psychological Review Monograph, 1920. 





PLaTE 5. Apparatus. used for reaction-time and rote memory. Note the char- 
acter showing at one of the windows of the memory apparatus. The apparatus 
itself is concealed by a special screen to avoid distraction of the subject’s at- 
tention. 





THE INFLUENCE OF TOBACCO SMOKING 89 


instant a word came into view, the timing part of the chronoscope 
was automatically set going. When the subject spoke the word, a 
sensitive voice key automatically stopped it. The reading of the 
chronoscope which had been taken before the word appeared, when 
subtracted from the reading taken after the response was given, 
yielded the time required for the reading of the word. 

The voice key used was patterned after one designed by Dunlap.’ 
It was supported by a standard in such a position that it was about 
an inch in front of the subject’s lips as he sat in his natural posi- 
tion before the exposure apparatus looking at the word. The ordi- 
nary vibrations of the subject’s voice were sufficient to set the 
delicate aluminum diaphram vibrating. This interrupted an elec- 
tric circuit which instantly stopped the timing part of the chrono- 
scope. Even with such a sensitive key there is always a certain, 
though small, amount of latency. But since this latency is the same 
in amount for the control days and the smoke days alike, it is auto- 
matically eliminated from the final results by our control technique, 
and its exact amount does not concern us. 

In order that no avoidable variability be introduced into the 
experimental results, the same 30 words were used throughout the 
experiment. But lest the subjects should gradually learn the order 
of the words and thus materially change the nature of the test, 36 
different bands were prepared on each of which the words were in 
a different chance order. Thus on each experimental day two differ- 
ent bands were used, each being used twice. Lest a constant error 
be introduced into the second and fourth tests of each day as a 
result of a familiarity of the order of the words already seen on 
the first and third tests, the second and fourth trials were always 
begun at widely different places on the band from the first. As a 
matter of fact the method of control used would have eliminated 
any such error from the final results had it existed. That no such 
tendency did result is shown very well by the fact that on the con- 
trol days the second test of each experimental day averages a little 


* This key consisted essentially of a stretched diaphram of aluminum foil 3.5 
inches in diameter and .oo1 inch in thickness. In the middle of this on the back 
is a very light platinum disk which is just touched by a platinum point with fine 
screw adjustment. 


90 CLARK L-HOULE 


slower in the case of both groups of subjects than the first (see 
Fig. 8). 

The complete results of the typical subject on reading reaction- 
time are shown in Table XXII. The construction of this table and 
the various computations are as described above p. 39 ff. He shows - 


TABLE XXII 


Reading reaction-time, subject No. 15, habitual smoker. Score, the time required 
to read a 4-letter word from an average of thirty, in units of .0034 sec. 


Difference between normal of day 












































Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I II LOL IV II III IV Difference 
days: (Normal) 

Nov. 8 172.3 170.4 1782 1774 +19 —59 —51 — 3.03 
SF L10 169.5 179.5 182.5 179.3 —100 —13.0 —9.8 —10.93 
dy Sa in E 166.4 171.6 1745 1684 —52 —81 —2.0 — 5.10 
eS 164.3 171.1 170.8 169.4 —68 —65 —51 — 6.13 
eae 161.0 168.1 169.8 1715 —71 —88 —10.5 — 8.80 
ae LS 170.0 171.6 175.4 2014 —16 —5.4 —314 —12.80 
Sal 9 194.7 162.9 170.2 162.7 +3818 +245 +32.0 -+29.43 
HDD 158.1 161.4 164.0 1709 —33 —59 —12.8 — 7.33 

Total 1356.3 1356.6 1385.4 1401.0 — 38 —29.1 —44.7. —24.69 

Average 169.53 169.57 173.17 175.12 — .04 — 3.63 — 5.59 — 3.08 

Me EVES Ree ere idocc ae ede eh Nite 8.44 7.04 10.54 8.15 

|S Sep aa ar the ara ey ce oy i 2.52 2.10 3.15 2.43 

Tobacco 
days: 

Nov. 7 172 ol Seb ee Sei 1096 — 88 —10.0 — 6.9 — 8.56 
raat!) 166.5 170.1 173.0 1748 —36 —65 —83 — 6.13 
ee eat by 159.6 167.9 170.38 167.4 —83 —10.7 —7.8 — 8.93 
ah A 156.6 161.8 177.6 166.3 —5.2 —210 — 9.7 —11.96 
SL 1°73:9- 165.3. 176.02 16.8 + 8.6 —2.2 — 2.9 + 1.16 
Cee 167.2 163.9 165.3 1590 +33 +19 + 8.2 4.46 
HEOTY) 169.1 159.4 169.3 148.6 + 9.7 — 2 +20.5 +10.00 
Seok 159.7 162.0 1585 1615 —23 412 -—18 — .96 
“ 23 =e 4 panes oe A EAS Ae es pues 

Total 1325.3 1331.9 1372.8 1334.0 — 6.6 —47.5 — 8.7 —20.92 

Average 165.66 166.49 171.60 166.75 — 82 — 5.938 — 1.09 — 2.61 

Mati Vea ee PE ee ie nates 6.02 6.11 ead: 6.28 

Pale be us ceaiccain anos oie vine ae eee 1.80 1.84 2.3 1.88 

Effect of 

Tobacco: 

Difference ioe walloouctickic fae eae — 78 —230 +45 + 47 

Pith sas se stam aanenas aioe te oeary 3.00 2.79 3.9 3.07 

Ratio! Bi ae Reser aeons coe ae .26 82 1.15 153 

Reliability” Aas 2a os oes eres saa 567 £705 781 54 


Per. cent gain/ot' 1058. 2.27). 205 «74s ae nae — 46 —1387 + 2.68° + 28 


oI 


THE INFLUENCE OF TOBACCO SMOKING 


























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AIXX FTV 


THE INFLUENCE OF TOBACCO SMOKING 93 


no reliable effect of smoking, though his final average takes the 
form of a minute gain in speed. 

The final results of the non-smokers and the habitual smokers 
are shown in Tables XXIII and XXIV respectively. A glance at 
the signs in the body of these tables reveals a striking lack of 
agreement among the various subjects as to the effect of the to- 
bacco, though in both tables there will be found a slight majority 
of plus signs. The final averages of both groups agree also in 
showing a slight stimulation as the result of smoking, though none 


200 


190 


180 


170 


Reading reaction-time in units of .0034 seconds 





Number of test 


—— Tobacco days —-=—-—Control days 


Fic. 8. The effect of smoking on the speed of reading four-letter words. Two 
upper curves, habitual smokers; two lower curves, non-smokers. 


04. CLARK L. HULL 


of the average differences approach even remotely to a satisfactory 
statistical reliability. 

The average course of the reaction-time throughout the experi- 
mental day was also computed for both groups of subjects sepa- 
rately and for both the tobacco and the control days. The group ~ 
of habitual smokers turns out, on the average, somewhat less 
efficient (i.e., slower) than the non-smokers. While the statistical 
reliability of this difference shows that it has no significance as to 
any permanent effects of tobacco, it is large enough to permit the 
control and drug curves of both groups of subjects to be shown 
in the same figure without interference. They appear in Fig. 8. A 
careful examination of these two sets of curves reveals a striking 
similarity between them. In each there is a marked separation of 
the drug from the control curve at the first post-dosage test. This 
is followed in each case by an approach of the two curves on the 
second post-dosage test, only to be succeeded on the last test by a 
divergence as great as the first. Despite the low statistical reliabili- 
ty of these differences, the marked agreement of the two sets of re- 
sults, particularly when taken in connection with other results of 
strikingly similar nature to be met with in subsequent chapters, 
furnishes some grounds for the belief that the peculiarities in the 
results noted above, may indicate a real tendency. This would mean 
that under conditions of the present experiment, smoking may 
produce a certain immediate effect, which later subsides, only to 
recur once more with an intensity more or less approaching that 
of the original effect. This hypothesis will be referred to from time 
to time as other evidence is encountered. An attempt at a possible 
explanation will be made in the final chapter of the monograph. 

The final summary and evaluation of the results of the present 
investigation will be reserved until the end of the following 
chapter. 


CHAPTER X 


THE EFFECT OF SMOKING ON THE SPEED OF ORAL REACTION 
TO FRESHLY LEARNED MATERIAL 


In the last chapter we considered the effect of smoking on the 
rapidity of the functioning of thoroughly formed ocular-vocal as- 
sociative bonds of long standing. In the present chapter we shall 
consider the effect of smoking on the rapidity of the functioning 
of ocular-vocal associative bonds which have just been established 
and which in strength are only just above the threshold of recall. 
The associative bonds in question were those formed in connec- 
tion with the learning test described in Chapter XIV. For this 
reason the description of the technique of the present experiment 
necessarily anticipates more or less what will be described in more 
detail there. The material consisted of fairly simple meaningless 
geometrical characters and nonsense syllables. Examples of the 
characters used are shown in Plate 6. One syllable was associated 
with one character by a prompting method in such a way that 
whenever the character appeared at the window of the exposure 
apparatus, the syllable would be spoken into the voice key by the 
subject. Psychologically, the test was very much like reading words 
of a foreign language without knowing their meaning. 

_ Only five of the characters and as many syllables were used on a 

given test. Six exact photographic duplicates of each character 
were provided. The photographs were cut up in such a way that 
each character was in the middle of a card about 34-inch square. 
These were attached to a canvas band, each with a drop of glue 
exactly as were the printed words in the test described in the last 
chapter. By means of the photographic duplicates the 5 characters 
were placed on the band in 6 different random orders, making 30 
entries in all. In the experiment, this band made two complete 
revolutions before the window of the exposure apparatus, instead 
of one as with the 30 words. Ordinarily the first revolution suf- 
ficed to establish the associative bonds between the characters and 


96 CLARK L. HULL 


their respective assigned phonetic values, well enough so that there- 
after when the subject would see a character at the window he 
‘could respond with the syllable without error. This left the second 
revolution of the band free for giving the reaction-times from this 
freshly learned material. During this second revolution, the ap- 
paratus and technique were exactly the same as described in Chap- 
ter IX for the 30 words. The reaction-times thus obtained consti- 
tute the data of the present investigation. 

A number of imperfections in the above method may now be 
mentioned. The first one lies in the well known fact that the speed 
of reaction at any given time, depends to a great extent upon the 
strength of the associative bond involved. Clearly, then, if the to- 
bacco should have a retarding effect upon the learning, say, the 
associative bonds during the second revolution of the band would 
be weaker than on the control days. This in itself would retard the 
reaction-time on the tobacco days entirely apart from any effect of 
the tobacco upon the speed of functioning of this kind of associa- 
tive bond as such. It is interesting to note, however, that the case 
where the most striking average effect of tobacco appears on the 
two processes under consideration, they are in exactly opposite 
directions. This suggests that the tendency noted above may have 
been so slight as to be negligible. 

A much more serious defect lies in the fact that some subjects 
learned so slowly that the promptings had to be extended far into 
the second revolution of the band. This reduced the number of 
reaction-times which could be obtained from certain subjects 
so greatly that their results had to be thrown out entirely. In the 
results of several others which are included in the final tables, tests 
now and then had to be thrown out for the same reason and in 
case the test chanced to be the first one of the day, the results of 
the entire day had to be discarded. And of the records actually 
used, many have less than the full 30 reaction-times for the same 
reason. Last of all may be mentioned occasional apparatus trouble. 
But it must be admitted that the general consistency of the final 
average results of this investigation is somewhat surprising in 
view of the irregularities just enumerated. Great care, however, 
was exercised in the scoring of the results, such as they were, and 


THE INFLUENCE OF TOBACCO SMOKING 97 


it is possible that the technique was really more reliable than it 
appears on the surface. 

The results of the typical subject are shown in detail in Table 
XXYV. It will be noted that the scores for November 7 and 23 were 


TABLE XXV 


Learning reaction-time, subject No. 15, habitual smoker. Score, average reac- 
tion-time on last 30 presentations of characters in learning test, in units 












































of .0034 sec. 
3 Difference between normal of day 
Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I Ii DET Vi su III IV Difference 
days: (Normal) 

Nov. 8 254.3 287.1 324.9 281.6  —32.8 —T0.6 —27.3 —43.56 

10 239.4 315.9 291.4 2361 —765 —52.00 + 3.8 —41.73 
eet 320.7 257.5 250.9 244.4 +63.2 +69.8 +763 -+69.76 
Salo 277.2 285.0 246.5 277.4 —7.8 -+30.7 — .2 -+ 7.56 
ae 6 253.8 248.3 269.6 217.4 +150 —63 +459 -+18.20 
ie 1S 249.6 244.8 258.3 267.38 4.48 —87 —17.7 — 7.20 
Hh TRE 250.4 219.38 271.7 253.7 +311 —213 —33 + 2.16 
22 283.4 255.1 264.2 293.6 +283 +19.2 —10.2 +12.43 

Total 2138.3 2113.0 2177.5 2071.5 +2538 —89.2 -+66.8 -+17.62 

Average 267.29 264.12 272.19 258.93 + 3.16 —49 + 835 + 2.20 

RB ie es urea aac wolbice cea ace 31.65 33.6 26.37 24.78 

ULL T) 2 en Oa AR ey Je > ee on 9.47 10.03 7.88 7.41 

Tobacco 
days: 

Nov. 7 — — — — — — —_ a 
ene 49 270.2 295.1 288.0 2653 —249 —128 +49 —10.93 
“ 19 313.0 288.8 266.7 2221 +242 +463 +90.9 +53.80 
rete W§ 222.3 214.8 272.1 307.32 4-75 %—49.8 —85.0 —42.43 
eel ty 229.4 286.2 206.7 210.7 —56.8 -+22.7 +18.7 — 5.13 
eka 289.4 288.9 2709 2459 + 6 +186 -+438.6 +20.93 
‘e209 233.2 199.0 2189 2449 +3842 4143 —11.7 +412.26 
eee: 250.9 216.2 194.4 250.9 +34.7 +56.5 0 +30.40 
“cs 23 — — aes. —- = Jl. en) pws. 

Total 1808.5 1789.0 1712.7 1747.1 +19.5 +95.8 +614 -+58.9 

Average 258.35 255.57 244.67 249.59 ay nail +13.68 + 8.77 + 8.41 

DN aN PME Rt RON i.e as cha tel avs.cko.«'a) en ie 6 ebis 5.56 25.79 36.25 23.92 

RMCANE ARI Pio s eke Coe ed els wears ooh 52) 16 8.23 11.57 7.62 

Effect of 

Tobacco: 

HE) RET ENCE IMM easter thaue race nie 6 sustenere'6. shale — 88 +1858 + 42 + 621 

WRIT i es ee a ae cats ye edins seeks eee hes 12.49 12.96 14.00 10.63 

Rationrere meee cee tas Oe aie Desc saheteels .03 1.43 .03 .584 

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IPegmcenticalirORm OSS ce avccaicn © csi en + — 24 4 707 + .16 + 2.36 


98 CLARKILSHULLS: 


so defective that they were thrown out. The construction of this 
table and the various computations are exactly as described on 
pp. 39 ff. and 49 ff. His final average, while somewhat erratic, 
shows in general a tendency to an increase in efficiency (speed) as 
the result of smoking, though the differences in no case approach 
a satisfactory statistical reliability. 

The final results of the influence of smoking on the speed of 
functioning of newly formed associative bonds, are shown for the 
non-smokers and the habitual smokers in Tables XXVI and 
XXVITI respectively. An inspection of the signs in the body of 
these tables reveals a striking lack of agreement among the various 
subjects as to the effect of tobacco, exactly as was found in the 
investigation of reading reaction-time. And also as with the read- 
ing, there is a slight preponderance of plus signs with both groups 
of subjects. The present results resemble those on reading-time 
also in that the final averages with both groups of subjects show a 
slight gain in speed of reaction as the result of smoking, though 
again this in no case attains a satisfactory statistical reliability. As 
a last point of resemblance, it must be pointed out that with both 
groups of subjects we find here also, on the second post-dosage 
test, the curious disappearance of the original effect with its subse- 
quent recurrence with original strength on the last test as noted 
on p. 94. 

With a view to getting further light on certain points, the aver- 
age course of the learning reaction-time throughout the experi- 
mental day was computed for both groups of subjects and for both 
the tobacco and the control days. These data are shown as parallel 
curves in Figures 9 and 10 for the non-smokers and the habitual 
smokers, respectively. As pointed out above, the reaction-time for 
weak associative bonds are much slower than for strong. The time 
required with the present material was about 50 per cent greater 
than that for reading the four-letter words. The present results 
have therefore been plotted to a correspondingly smaller scale so 
as to facilitate comparison. The curves of Figures 9 and 10 show 
perhaps a little greater irregularity than those of Fig. 8 which is 
to be expected from the irregularities in the present data already 
described. The usual slowness of the habitual smokers as compared 


THE INFLUENCE OF TOBACCO SMOKING 


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THE INFLUENCE OF TOBACCO SMOKING IoI 


340 


320 


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200 


Reaction-time in units of .0054 seconds 


180 





Number of test 


-—-=- Tobacco days =—=——Control days 


Fic. 9. The effect of smoking on the speed of reacting to freshly learned 
material, non-smokers. 


with the non-smoking group appears, but it has no significance as 
to any permanent effect of tobacco. Lastly a careful comparison 
of the present curves with each others and with those of Fig. 8 will 
show once more the peculiar rhythmical effect noticed in Chapter 
IX, to be common to all four pairs of curves. 

The present writer has been unable to find in the literature any 
experimental results as to the influence of smoking on reaction- 
time, though it is understood that an intensive investigation of 
this subject has been under way for some time. Accordingly our 


102 CLARK LAHULLE 


340 


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260 





5 


we) 
7 
fo) 


200 


Reaction-time in wits of .0034 seconds 


Number of test 


—— Tobacco days -———Control days 


Fic. 10. The effect of smoking on the speed of reacting to freshly learned 
material, habitual smokers. 


conclusions must be based entirely upon the results of the two in- 
vestigations here reported. They may be summarized as follows: 
1. The final averages from neither of the groups of subjects 
and from neither of the two tests yield a single effect of any kind 
which attains a satisfactory statistical reliability. ; 
2. It is noteworthy, however, that the final averages in all four 
cases agree in showing a small average gain in efficiency (speed) 
as the result of smoking—around 1%. This striking agreement 
under the variety of conditions lends to the four averages taken 


THE INFLUENCE OF TOBACCO SMOKING 103 


together, a reliability considerably greater than that shown in the 
tables where they stand alone. Roughly speaking, the probable 
error of all four sets of data taken together is only about half that 
for any one set alone. Under this assumption, the chances are 
around 15 to 1 that smoking causes a very slight stimulating effect 
on the speed of functioning of ocular-vocal associative bonds on 
the first and last post-dosage tests. 


CHAPTER XI 


THE EFFECT OF SMOKING ON THE SPEED OF CONTINUOUS 
MENTAL ADDITION 


In Chapter IX we considered the effect of smoking on the speed 
of the functioning of thoroughly formed associative bonds of a 
sensory-motor type. It will be observed that the physical element 
in that process is still fairly large. In the present chapter, we shall 
pass to the consideration of the effect of smoking upon the rapidity 
of the functioning of thoroughly formed associative bonds which 
are on the strictly mental level. The form of the addition test em- 
ployed was an adaptation of one described by Starch.* It is so com- 
pletely “‘mental” that it does not require even the writing down 
of answers by the subject. No apparatus is required. The subject 
takes up any comfortable position that he prefers. The experi- 
menter says “Ready,” starts his stop-watch and at the same time 
calls out a two-place number such as 26. The subject then proceeds 
to add to this the digit 6, to that total 7, to that total 8, then 6, 
then 7, then 8 and so on continuously as rapidly and accurately as 
possible, calling out the totals (only) as they are obtained. Thus 
the first few totals starting as indicated above would be: (26) 32, 
39, 47, 53, 60, 68, 74, and so on. When 100 is reached, the hun- 
dreds are dropped from the totals, the subject never speaking more 
than the first 2 digits. At the end of 30 seconds the experimenter 
interrupts the subject by speaking a new number—say 84. The 
subject immediately begins adding to this number the 6, 7, and 8 
as before and continues for 30 seconds, when a new number is 
given, and so on. The adding is continued for 5 minutes at each 
test and yields Io sets of additions. 

For recording the performance in this test, special mimeo- : 
graphed sheets were prepared containing in parallel columns the 
totals for the various starting numbers as far as 25 additions each. 
The experimenter would call out the number at the top of the 


1 Starch, D., Experiments in Educational Psychology, p. 172 ff. 


THE INFLUENCE OF TOBACCO SMOKING 105 


column and then follow along down the series of totals with his 
pencil as the subject spoke them until 30 seconds had elapsed, 
when he would draw a line beneath the last total given, at the same 
time calling out the number at the top of the next column. In case 
the subject made an error part may down the column as often 


TABLE XXVIII 


Adding, subject No. 15, habitual smoker. Score number of correct additions 
performed in five minutes. 


Difference between normal of day 


Original scores and subsequent <ests 
Test Test Test Test Test Test Test Average 
Control I II Tile why. II III IV Difference 


days: -(Normal) 


Nov. 8 123 144 1382 128 +21 + 9 + 6 +11.66 
ae LO 155 153 1386 166 — 2 —19 +11 — 3.33 
er iiee= 249 on itt 6163, 1b 2-2 ed + 5 2.3% 
als 157 153 156 154 — 4 —i1 — 3 — 2.66 
e016 187 178 185 182 —9 — 2 — 5 — 6.33 
Ls 198 206 183 201 + 8 —15 + 3 — 1.33 
a) 2 Oe 82068 e212 + 7 — 6 0 +. .383 
eae 228 239 207 225 +11 —21 — 3 — 4.33 

Total 1409 1489 13858 1422 +30 —51 +13 — 2.66 

Average 176.12 179.87169.75177.75 + 3.75 —637 +162 — 33 

NCA Vcde wee. x4 wip elaisin siats.#/5/6.9 rae 164 8 8.97 4.25 3.83 

PERN Has oe ea toes he Phe ees owas 2.39 2.68 1.27 1.14 

Tobacco 
days: 

Nov. 7 LOS mee LOL 2b eS + 7 +22 +15 +14.66 
ae BY 165 140 148 158 —25 —17 —7 —16.33 
Nae: UII ee Li3y eLS2e 1S8L — 6 + 3 + 2 — .33 
ie Le 172 #198 192 £190 +26 +20 +18 +21.33 
meeLo 192 194 190 200 + 2 — 2 + 8 + 2.66 
Suet Z 197 218 205 200 +21 + 8 +3 +10.66 
ee 0 286. 226 221 209 —10 —15 —27 —17.33 
ral 206 224 229 217 +18 +23 +11 +17.33 
YR 222 2386 . 227 241 +14 + 5 +19 +12.66 

Total 1672 1719 1719 1714 +47 +47 +42 +45.33 

Average 185.77191 191 190.44 + 522 +522 +4 466 + 5.03 

TSM VeMi er tteier octets 6 oie sfaieis eae osc aictt ore 13.30 11.60 10.60 11.40 

RNa tie FO oid sae vielo'e Saiesle vanes 3.75 3.27 2.99 3.21 
Effect of 
Tobacco: 

PUatreTeNnCe oe Pieces alee ee vs Maeelak +147 +1159 + 3.04 -+ 5.36 

RET SMe aie s pnieidics ces s:0' ae 4 spelen’ 4.45 4.23 3.25 3.41 

RAUIOMerrsie since crc.e risers 8 ores ee e.ai a's 33 2.74 .94 1.57 

Pe CHA DIET VERS: |. ss cio aia aio’ inc p site's oe 593 .968 2109 .859 


Pericent wait) Of 10SS. Js scarves ves + 81 | + 640 +168 -+ 2.96 


106 CLARK EeHULL 


happened, the experimenter recorded the incorrect total on the 
sheet by the side of the corresponding correct one and beneath 
this in a column all the following totals given during the remainder 
of the half minute. This was necessary because, once an error is 
made, all the remaining totals will differ from the printed series 
even though all the subsequent additions be correct. Occasionally 
very rapid adders succeeded in making more than the 25 additions 
in the allotted 30 seconds, in which case the additional totals given 
were recorded beneath the appropriate column. The score in this 
test is the total number of correct additions performed in the 5 
minutes. The score on errors will be considered in detail in Chap- 
ter XII. 

The results of the typical subject on speed of adding are shown 
in detail in Table XXVIII. The construction of this table and the 
various computations are exactly as described on pages 39 ff. and 
49 ff. This subject shows a fairly consistent increase in the rate of 
addition as the result of smoking. One of the differences attains a 
satisfactory statistical reliability. 

The final results with the present test reveal perhaps the most 
interesting and important effects of smoking found in the entire 
investigation. The final averages are shown in Tables XXIX and 
XXX for the non-smokers and the habitual smokers respectively. 
An inspection of the results with the non-smokers shows, with a 
single exception, a consistent loss in efficiency (speed) as the re- 
sult of smoking. The habitual smokers, on the other hand, show a 
uniform gain in efficiency with no exception whatever. The sta- 
tistical reliabilities of all averages with both groups of subjects are 
practically perfect. Despite these high reliabilities, however, the 
effects themselves are not excessive. The loss in efficiency among 
the non-smokers averages —2.77 per cent for the post-dosage 
period, while the gain among the habitual smokers averages +5.21. 
It is also important to note that the bad effect on the non-smokers 
shows no signs of subsiding at the close of the experimentai 
day (approximately 1 hour and 15 minutes after the dose) and the 
stimulating effect on the habitual smokers seems to be slightly in- 
creasing. 

In order to secure further light on the above results, the average 


107 


THE INFLUENCE OF TOBACCO SMOKING 


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THE INFLUENCE OF TOBACCO SMOKING 109 


240 


210 


=) 
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Number of correct additions performed in five minutes 
oO 
o 





Number of test 





Tobacco days —-- Control days 


Fic. 11. The effect of smoking on the rate of adding. Two upper curves, non- 
smokers; two lower curves, habitual smokers. 


course of the rate of adding throughout the experimental day was 
computed for both the smokers and the non-smokers, and for the 
drug and control days separately. The results for both groups of 
subjects are shown in parallel in Fig. 11. As usual we find the 
habitual smokers, on the average, somewhat less efficient than the 
non-smokers. The difference in this case amounts to about 17 per 
cent. Its reliability is only .890 however, so that it has no particular 


110 CEARKOLSAULL 


significance. Turning our attention to the respective pairs of 
curves, we find them showing excellent consistency. The drug and 
control curves in each case originate from practically the same 
point. Thereafter there is a distinct separation, opposite in direc- 
tion in the two cases, which is maintained to the end of the ex- 
perimental day. 

The results of the present investigation my briefly be form- 
ulated as follows: 

1. Among non-smokers, smoking causes a very consistent loss 
in rate of adding, averaging —2.77 per cent. 

2. While not large, this loss in efficiency seems to be rather 
durable, since there are no signs of recovery 1 hour and 15 minutes 
after the termination of the smoking. 

3. Among the habitual smokers, on the other hand, anata 
causes with great regularity a gain in the rate of adding amount- 
ing, on the average to -++5.21 per cent. 

4. With the habitual smokers, also the effect seems to be un- 
usually persistent, there being again no sign of a return to normal 
at the close of the experimental day. 

5. Habituation seems, therefore, definitely and completely to 
have reversed the effect of the drug with respect to this particular 
test. 

A number of different investigators have reported results bear- 
ing on the relation of smoking to the rate of adding. Before pro- 
ceeding to the consideration of these results however it must be 
noted that the form of the adding test used in securing them differ- 
ed in certain respects from that used in the present experiment. In 
all the previous investigations the subjects have added short col- 
umns of figures and recorded the totals themselves. In the present 
experiment, on the other hand, the numbers to be added were never 
seen by the subject at all but must instead be held in mind by him 
continuously in their recurring order as described above. These 
complexities added to the already complex mental processes of ' 
ordinary addition probably made the present method somewhat 
more exacting in its demands upon the attention of the adder. 
Even so, there appears to be rather good agreement between the 


THE INFLUENCE OF TOBACCO SMOKING III 


present results and those of previous investigations. Froeberg? in 
a fairly well controlled experiment, found 5 non-smokers averag- 
ing a loss in efficiency of —5.9 per cent. This agrees with the re- 
sults of our own non-smokers though it it somewhat larger in 
amount. Berry,*® on the other hand, found with himself (habitual 
smoker) a gain in efficiency of +6.3 per cent.* This is in substan- 
tial agreement with our results from habitual smokers. Johnson® 
also reports a small amount of evidence suggesting that smoking 
improves adding efficiency though he does not state the smoking 
habits of his subjects. Bush,*® however, reports results in complete 
disagreement. He found with a group, chiefly habitual smokers, a 
loss in adding efficiency as the result of smoking of —9 per cent. 
Unfortunately, as pointed out above, the technique of Bush’s ex- 
periment is open to such question that it is difficult to say how 
much weight should be attached to his results. The present writer 
is inclined to discount them rather heavily. Assuming this view to 
be sound, the indication of the available evidence as to the effect 
of smoking on adding efficiency is pretty clear. It decreases some- 
what the efficiency of non-smokers but quite markedly increases 
that of the habitual smokers. 

But before accepting the above formulation as final, we must 
give careful consideration to a fundamental question which has 
been latent wherever we have considered the results from habitual 
smokers—that of withdrawal or privation effects. That marked 
effects are produced in subjects who are accustomed to the use of 
certain habit-forming drugs when the usual dose is withheld for 
some time, is well known.” These effects are ordinarily in the 
direction of a loss in functional efficiency. The question therefore 
rises insistently at this point: Were the post-dosage scores on the 
drug days superior to those on the control days because of an 
inherently stimulating action of the tobacco on the drug days, or 
because of a depressing effect caused by the Jack of the accustomed 

2 See p. 14 above. 

8 See p. 13 above. 

4 See Appendix F. 

5 See p. 13 above. 


6 See p. 12 above. 
7 Pettey, G. E., Narcotic Drug Diseases, pp. 13-14, also 304-305. 


112 GEARKS DRrGia: 


dose on the control days? The question is an extremely difficult 
one but it is so fundamental for the interpretation of the results of 
the habitual smokers that it must at least be faced squarely and in 
the light of whatever evidence is available. Fortunately the present 
investigation yields a considerable number of parallel records from - 
the same set of habitual smokers in a variety of mental functions, 
as well as corresponding records from a group of non-smokers 
who, for the present purpose, may be considered as a kind of con- 
trol squad. 

The first question to be considered is the extent of withdrawal 
of the drug which actually took place on the control days. It will 
be recalled (Chapter II) that on these days the subjects received no 
tobacco during the experiment though the nature of the control 
dose was such that they were led to believe that they did. This fact 
served to eliminate any pseudo withdrawal effects which might 
have resulted from autosuggestion. Moreover, being keenly aware 
of the danger from withdrawal effects from the first, the writer 
planned the technique of the experiment with the express intention 
of eliminating them so far as possible. To this end the second 
squad of subjects was limited almost entirely to pipe rather than 
cigarette smokers because the former, while probably consuming 
as much tobacco in the aggregate, take it at considerably longer 
intervals. This fact made it possible without disturbing their 
regular smoking habits, to have them report to the laboratory with- 
out having smoked for at least 3 hours preceding arrival. Their 
habits, however, usually did call for a smoke at about the time the 
first test was given or a little before, it being shortly after a meal. 
Therefore the first test where any particular withdrawal effects 
might be expected would be the first post-dosage test. The duration 
of the withdrawal at this stage would be about an hour or a little 
more, while that for the last post-dosage test would be between 
2% and 3 hours. 

The next question to be considered is whether, as amatter of fact, 
this amount of withdrawal actually did produce privation effects 
with the habitual smokers ? For reasons given in the last paragraph 
it is assumed that the score on the pre-dosage test is free from any 
noticeable withdrawal effects. Then if any such effects exist, they 


THE INFLUENCE OF TOBACCO SMOKING 113 


should manifest themselves either as a falling off of the score 
during the post-dosage period from the level set by the pre-dosage 
test or at least by a relative falling off as compared with the cor- 
responding pre- and post-dosage scores of subjects clearly free 
from any such suspicion of withdrawal effects in the control scores 
of the non-smokers. And while it would perhaps be rash to say that 
the average course of performance in the various tests would be 
identical for these two groups of subjects except for possible 
withdrawal effects, a consistent difference between them in one 
direction or the other may quite properly constitute a presumption 
in favor of, or against the existence of such effects. As an example 
of the difference in question, the non-smokers on the control days 
showed an average slump on the post-dosage tests in reading reac- 
tion-time of about 3 points. The habitual smokers under similar 
conditions, also show a slump, but only 1 point. This gives the 
habitual smokers an advantage of about 2 points. There is thus no 
indication of a pernicious withdrawal effect here and the pre- 
sumption is distinctly against it. 

For the purpose of getting as comprehensive a view of this 
matter as possible, the results from the 7 tests in which reliable 
results are available from both groups of subjects have been as- 
sembled in Table XXXI. An inspection of the last two columns of 
this table shows that out of the 6 strictly mental tests, only one 
(adding) shows any tendency whatever in the direction of a per- 
nicious withdrawal effect. If we include tapping, a strictly physical 
test which happens to show a loss, the average effect in the entire 
group of 7 tests is a gain of 4.35 per cent. There is thus quite 
clearly no general tendency to a loss in functional efficiency on the 
part of the habitual smokers as the result of failure to receive the 
accustomed dose of tobacco on the control days. But granting this, 
it is still noteworthy that the one exception among the strictly 
mental tests in the above table is the very one for which we have 
been seeking an explanation. This coincidence raises the question 
at to whether pernicious withdrawal effects may take place in one 
test, at the same time leaving other tests quite undisturbed? This 
seems rather unlikely, though perhaps it may be no more remark- 
able than that one mental function should be stimulated while at 


CLARKE AHGLL 


114 





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IXXX THUVL 


THE INFLUENCE OF TOBACCO SMOKING 115 


the same time another is depressed by the same drug and in the 
same subject. 

Turning now to a detailed consideration of the data in question 
(Table XXX and Fig. 11) we find little evidence of an absolute 
falling off in the rate of adding during the post-dosage period. 
The curve is practically horizontal throughout the experimental 
day, though computation reveals a minute falling off of 1.04 ad- 
ditions per 5-minute period—about %4 of I per cent. But during 
the same period the non-smokers show a gain of 4.82 additions. 
Thus the loss of the habitual smokers (5.86 additions or about 
2.9 per cent) is almost entirely a relative one. But this does not 
nearly account for the apparent stimulation of the habitual smok- 
ers following the dose on the drug days. An examination of this 
curve shows that it rises distinctly more than even the control 
curve of the non-smokers. This rise represents an average gain 
of 8.91 additions as compared with one of 4.82 for the non-smok- 
ers for the post-dosage period. Thus, even under the rather dubious 
assumption that mental addition would show a pernicious with- 
drawal effect while all the other mental tests show rather an op- 
posite tendency, approximately half of the apparent stimulation of 
the habitual smokers is still unaccounted for. But even after mak- 
ing this deduction, the statistical reliability is such that there is 
still only about 1 chance in 1000 that there is not a real stimulation 
of adding with these subjects as the result of smoking. 

Taking all the available evidence into consideration, then, the 
indication is quite clear that the smoking of a pipe of tobacco de- 
creases somewhat the adding efficiency of non-smokers but in- 
creases that of habitual smokers. 


CHAPTER XII 


Tue EFFECT OF SMOKING ON THE ACCURACY OF CONTINUOUS 
MENTAL ADDITION 


The technique of the adding test has been fully described in 
Chapter XI. The score of accuracy in this test was the number of 
incorrect additions made during each 5-minute period. Errors 
made but spontaneously corrected by the subject were not counted. 
At least two types of error may be distinguished: (1) actual in- 
correct additions, and (2) cases where the wrong digit was added 
because of momentary confusion as to the sequence of the 6, 7, 
and 8. The two types appeared to be about equally common though 
no systematic observations were made on this point. The scoring 
of the first type was simple. But in cases where two or more ap- 
parent errors came in immediate succession, an examination was 
always made to ascertain whether the subject had gotten out of 
step in the sequence of the digits to be added. If the additions im- 
mediately following were such as to indicate this, the new order 
was assumed and the following totals were counted as correct, as 
long as consistent with it, the first addition only of the new series 
being counted an error. 

The detailed scores showing the effect of smoking on the ac- 
curacy of mental addition of a typical subject are shown in Table 
XXXII. The construction of this table and the various computa- 
tions are exactly as described above, page 39 ff. This subject shows 
as the result of smoking a loss in efficiency throughout the post- 
dosage period. On the first post-dosage test the loss attains a 
satisfactory statistical reliability. The absolute effect is small but 
the percentage effect is large. The latter is due to the small number 
of errors made during any 5-minute period. 

The final results of the effect of smoking on the accuracy of 
continuous mental addition is shown in Tables XXXIII and 
XXXIV for the non-smokers and the habitual smokers respective- 
ly. An inspection of the signs in the body of these tables shows at 


THE INFLUENCE OF TOBACCO SMOKING 117 


once that there is no uniformity in the nature of the final averages 
from the various individual subjects. The final averages from the 
non-smokers as a group, however, show a tendency to a loss in 
efficiency as the result of smoking, though in no case does the 
effect get large enough to attain a satisfactory statistical reliability. 


TABLE XXXII 


Incorrect addition, subject No. 15, habitual smoker. Score, number of errors 
made in five minutes of continuous addition. 


Difference between normal of day 


Original scores and subsequent tests 
Test Test Test Test. Test Test Test Average 

Control it! II III IV II III IV Difference 
days: (Normal) 

Nov. 8 15 oT), 7 —s +4 A283 + 6.66 
eel 0 ill 8 9 8 + 3 +2 + 3 + 2.66 
pint 9 9 10 8 0 —1 +1 0 
ee LS. 2 7q = 3 — 5 —1 —1 — 2.33 
“ 16 8 4 5 1 te 4 8 a + 4.66 
eis > 4 5 2 3 eT +2 ai He .66 
et 9 2 1 1 a +1 +1 +1 + 1.00 
eae2a 3 4 5 0 pant a png 0 

Total 4 45 46 31 +9 +8 +23 +13.33 

Average 6.75 —6.62 6.75 3.87 +112 +4100 + 287 -+ 1.66 

VS Vat sac este Ea Ee Ga ee cere 2.91 1.75 2.38 2.23 

Ree eat al vik cece oe mice eae 87 52 Ariat 67 

Tobacco 
days: 

Nov. 7 20 20 17 13 0 +3 +7 + 3.33 
oe 9 4 18 9 8 —14 —5 — 4 — 7.66 
ae Le 9 13 6 10 —4 +3 —1 — .66 
one 4: 6 8 9 8 — 2 —3 — 2 — 2.33 
haha 4 9 tf 4 — 2 0 + 3 + 33 
ae 3 2 2 3 PEA +1 0 + .66 
SaeaO: a! 2 2 4 —l1 —1 — 3 — 1.66 
3 6 2 2 0 4 +4 cere + 4.66 
“« 23 4 4 1 3 0 aa ed SP 98 

Total 6078 656 68 Sa +5 a 2,00 

Average 6.66 8.66 6.11 5.89 —2?00 +6 + 78 — 22 

1 Bey OS sates CRE Ce SEEMED ERICEIRA IC eal 2.49 5.31 2.54 

Be ac aoe oe by ko Siglo bo uss 88 70 1.50 72 

Effect of 

Tobacco: 

HA LErCTICGMENGG Soret e vine cic se ss! e.a ofere aise — 312 — 46 —209 — 188 

LDS Ae, BR eer ce ie 1.24 87 1.66 .98 

PRETO ATE Tete dr cvove niaines asuelie en sieaseseiouave-o 2.53 52 1.26 1.92 

Sees eRe wie sls. sra vv clelaa tem mele ss OF 9541 6321 781 


: 91 
Percent gait or Joss\ic. ie. ee. 2056s —16.56 —6.71 —31.19 —28.06 


118 CLARK EV HGLE 


It will be recalled that this set of subjects also showed a loss in the 
rate of adding. The habitual smokers, on the other hand, average 
practically zero in effect and the statistical reliabilities are quite 
negligible. 

In addition, the average number of errors made on the various 
tests throughout both the tobacco and the control days, were com- — 
puted for both the non-smokers and the habitual smokers. These 
are shown in parallel curves in Figures 12 and 13 respectively. 
The marked difference in the points of beginning of each of these 


12 


Wumber of errors in five minutes 





Number of test 





Tobacco days —-—-Control days 


Fic. 12. The effect of smoking on accuracy of adding, non-smokers. 


Number of errors in five minutes 





Number of test 





Tobacco days —-——Contrel days 


Fic. 13. The effect of smoking on accuracy of adding, habitual smokers. 


119 


THE INFLUENCE OF TOBACCO SMOKING 

































































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AIXXX SVL 


THE INFLUENCE OF TOBACCO SMOKING 121 


pairs of curves suggests a marked variability and, in so far, un- 
reliability of the present data. This is quite in harmony with the 
striking lack of agreement in the results of the various individual 
subjects already noticed and with the low statistical reliabilities 
despite fairly large percentage effects, found in the averages from 
the group of non-smokers. This is probably due in the main to the 
small number of error made in any 5-minute period, too small in- 
deed for thoroughly adequate measurement. It should be noticed, 
however, that both pairs of curves agree in suggesting a general 
loss in efficiency as the result of smoking though it would be quite 
impossible to say how much or indeed with any certainty whether 
it causes any loss at all. The likelihood of a loss in efficiency among 
the habitual smokers is much less than with the non-smokers. 

The only writer who has reported results in errors in addition is 
Berry. He states that smoking improved accuracy with him, but a 
recomputation of his results (Appendix F) which eliminated a 
constant error in them due to practice effects, shows that no effect 
whatever resulted. This agrees substantially with the results of 
the habitual smokers in the present investigation. 

We may summarize the evidence as to the effect of smoking on 
the accuracy of mental addition, by saying that there is a little 
reason to believe that accuracy is slightly lessened with non-smok- 
ers but the evidence is quite indecisive in the case of the habitual 
smokers. If there is an effect among the latter it is too slight to be 
measured by the present methods. 


CHAPTER XI 


THE EFFECT OF SMOKING ON THE AUDITORY MEMORY 
SPAN FoR DIGITS 


In the last four chapters we have been dealing for the most part 
with the influence of smoking on the efficiency of the functioning 
of associative bonds already established. In the present chapter 
and the following one, our interests shall be directed in the main 
to the influence of smoking on the ease or rapidity of the original 
formation of associative bonds. The present one in particular will 
be devoted to the consideration of the rather short-lived bonds 
which are established through the single hearing of a digit series, 
and which are retained little longer than is required to repeat the 
series orally. It should be noted, however, that the mental process 
in question is a complex one and that it involves many other 
factors, among the more important of which are the memory after- 
image and steadiness of the attention. For this reason it it impos- 
sible to say with certainty which of the various factors may be 
primarily responsible for any effects which may be observed. 

The technique of giving the test was very simple. The subject 
was seated comfortably in a swivel chair about 4 feet in front of 
the experimenter. After a warning signal, the experimenter began 
repeating in a loud clear voice at the rate of one a second, a special- 
ly prepared series of digits, letting the voice fall on the last of the 
series. The falling of the experimenter’s voice was the signal for 
the subject to begin repeating the digits so far as possible in exact- 
ly the order heard. Ten such trials were given at each test. The 
score was the number of series out of the ten which were re- 
produced without error. Spontaneous corrections were permitted. 
The experimenter was specially trained to give the digits at the ° 
right tempo and as an added precaution, he tested himself fre- 
quently in this respect by means of a stop-watch which always lay 
before him while giving the test. 

In all, about 300 series of digits were utilized. As a consequence 


THE INFLUENCE OF TOBACCO SMOKING 123 


the use of a given digit series was relatively infrequent, which 
adequately guarded against any tendency to permanent learning 
of the material. The series were constructed in the following man- 
ner: The 9 digits were written on small cardboard disks which, 
after thorough mixing, were drawn out at random and written 
down. All series which chanced to obtain any of the more familiar 
number progressions such as 2, 4, 6 and the like, were returned to 
be drawn over. After the 9 digits of each series were recorded, 3 
more digits were added at the end of each, making 12 in all. These 
of course had appeared in the series already. In order that the re- 
petition should appear as little conspicuous as possible, the 3 ad- 
ditional digits were so chosen that they had not appeared either 
as the first or as the last two of the original series of 9. The various 
series were typed for use in parallel columns of Io series each. In 
order to aid the experimenter’s eye, where, as usual, less than 12 
digits were being used, vertical lines were drawn in such a way 
as to separate the eighth digit from the ninth and the tenth from 
the eleventh. : 

In order for a test like the present one to succeed, it must be 
difficult enough so that the subjects will always fail on some of the 
trials yet easy enough so that they will always be able to get a con- 
siderable number correctly. Owing to the marked differences 
among individual subjects and to the great changes in each sub- 
ject due to practice, a rather flexible system had to be devised so 
that these conditions should at all times obtain. Since the results 
of the first experimental day were always discarded, this day was 
utilized to discover as accurately as possible the length of digit 
series that a given subject could repeat correctly about 7 trials 
out of 10. Suppose this was found to be about 8 digits. Then the 
subject in question for the following few days, would be given at 
each test 5 series of 8 digits followed by 5 series of 9. If at the 
end of 4 days, say, practice had improved his score so that it 
threatened to exceed the desired limits, the test would be changed 
to 5 series of 9 digits followed by 5 series of 10. The number of 
digits in the series was of course always the same throughout any 
given experimental day. And, while perhaps not absolutely neces- 
sary owing to the system of computation, an additional precaution 


124 CLARKE HULE 


against possible constant error was provided by the fact that 
changes from one length of digit series to a more difficult one were 
always made on a date such that the same number of tobacco and 
control days had been tested with the length of series about to be 
discarded. The reason for giving series of two different lengths — 


TABLE XXXV 


Memory span for digits, subject No. 15, habitwal smoker. Score, the number 
of perfect responses out of ten trials. 


Difference between normal of day 


Original scores and subsequent tests 
Test Test Test Test Test Test Test Average 

Control I II LODE MARY II III IV Difference 
days: (Normal) 

Nov. 8 6 5 9 6 —1 + 3 0 + - .66 
ran 1) o 2 f( 6 —i1 + 4 + 3 -+ 2.00 
pephi nr ede Tedd +2 +5 a3 + 3.00 
eta 46 a6 sas eg aug iI + 1.66 
“ 16 6 9 4 8 + 3 — 2 + 2 + 1.00 
S518 8 9 8 7 +1 0 —i1 0 
19 6 10 7 8 + 4 +1 + 2 + 2.33 
22 8 8 qf 9 0 —1 +1 0 

Total 43 53 55 53 +10 +12 +10 +10.66 

Average 5.37 662 687 662 +125 4+ 15 +125 + 133 

IMR V Re eee oct s eh EL eee 1.50 2.0 1.00 92 

Perdue Ss titdceetsihe grate eaieiaee .448 598 .299 275 

Tobacco 
days: 

Nov. 7 7 5 5 8 — 2 — 2 +1 — 1 
eSNG 3 3 4 2 0 +1 —i 0 
Le ay be 5 5 7 6 0 + 2 +1 +1 
a4. 5 4 3 3 — i — 2 — 2 — 1.66 
seni 4 4 8 4 0 + 4 0 + 1.33 
ae 17, 9 5 qT 3 — 4 — 2 — 6 —4 
a0 5 qT 9 8 + 2 + 4 + 3 + 3 
Ly HE Wh i 9 7 0 + 2 0 + .66 
re: 9 8 8 6 —i1 —1 = 3 — 1.66 

Total 54 48 60 47 — 6 + 6 — 7 — 2.33 

Average 6 5.33 6.66 5.22 — 66 + 66 — 27 — 26 
RA Ee Wead eI ER TOR ORR Ne nce 1.18 2.15 1.97 1.62 

Pe Higysasahes cavceteatea mm cre 332 .606 555 .456 

Effect of 

Tobacco: 

Difference wm voas ace perder oen ae eee —191 — 84 —202 — 1.59 

Pi. Hy ttewcs 2 ets aula eaten aver ne anes .56 85 63 53 

Ratiotes 2 chi vitae ele hla ci ctoke tote talers 3.42 .99 3.21 2.99 

Reliability. -so.cn ciape wane acae: 9891 £7392 .9845 9767 


uf : 
Per cént gain Of 10SS\..52. 004s <5 —33.62 —14.79 —35.56 . —27.99 


THE INFLUENCE OF TOBACCO SMOKING 125 


at each test was to so widen the range of the test that whatever 
the effect of the drug, of practice or of accidental factors, the sub- 
ject would still be able to succeed on some of the trials yet never 
on all of them, thus conforming to the principles laid down at the 
beginning of the paragraph. 

Lastly, because of the auditory nature of this test, special care 
was exercised in the choice of subjects, all prospective ones being 
eliminated who were suspected of being in any way defective in 
hearing. _ 

The detailed scores showing the effect of smoking on the audi- 
tory memory span of a typical subject are shown in Table XX XV. 
The construction of this table and the various computations are 
exactly as described on page 39 ff. This subject shows a loss in 
efficiency throughout the post-dosage period. The differences at 
two of the three tests show a satisfactory statistical reliability. 

The final results of the present investigation are shown in 
Tables XXXVI and XXXVII for the non-smokers and the ha- 
bitual smokers respectively. In regard to the individual non-smok- 
ers, an inspection of the signs on the first and third post-dosage 
tests shows a decided preponderance of losses in efficiency as the 
result of smoking. The final averages from these subjects as a 
group show a loss in efficiency throughout the entire post-dosage 
period, the differences on the first and third post-dosage tests 
attaining a distinctly satisfactory statistical reliability. The in- 
dividual habitual smokers also show a slight preponderance of 
losses in efficiency on the first and third post-dosage tests, but less 
than the non-smokers. Their final averages as a group shows a loss 
throughout the post-dosage period, particularly on the tests just 
mentioned though they are distinctly less in amount than with the 
non-smokers and none of them approach satisfactory statistical 
reliability. It will also be noted that the second post-dosage test 
with both groups of subjects shows a decidedly smaller effect than 
either the first or the third. It will be recalled that this anomaly 
has been observed on several previous occasions. 

The average number of perfect responses on the various tests 
throughout both the control and the tobacco days was also com- 
puted for both the non-smokers and the habitual smokers. These 


CLARK L. HULL 


126 





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— _e eee 


Number of digit series repeated correctly out of ten trials 





Number of test 





Tobacco days === Control days 
Fic. 14. The effect of smoking on auditory memory span, non-smokers, 


are shown in parallel curves in Figures 14 and 15 respectively. The 
pairs of curves in the two figures resemble each other in a most 
remarkable manner. In the first place the two curves of each pair 
originate from practically the same point, the closely similar origin 
arguing well for the general reliability of the results. What differ- 
ence there is, in both cases is in favor of the control days. More- 
over, in both figures the control curves rise somewhat in the course 


THE INFLUENCE OF TOBACCO SMOKING 129 


Number of digits repeated correctly out of ten trials 





1 2 3 4 
Number of test 





Tobacco days —---Control days 
Fic. 15. The effect of smoking on auditory memory span, habitual smokers. 


of the experimental day, the rise of the habitual smokers being 
somewhat greater. Lastly, the drug curves in both cases decline 
on the first post-dosage test, rise markedly on the second post- 
dosage test and finally fall again on the last test. The relative levels 
of the control curves of the two groups of subjects have, in this 
case no relation to their respective abilities in auditory memory 
span, since the general level of the score with all subjects was set 


130 CLARK LAGULLE 


more or less arbitrarily by the experimenter as already described 
(p. 123). 

The results of the investigation may now briefly be summarized: 

1. The non-smokers show an unmistakable loss in efficiency 
in memory span as the result of smoking. 

2. This is apparently as great 1 hour and 20 minutes after the 
dose as immediately after. : 

3. Despite the low statistical reliabilities of the final averages 
of the habitual smokers as a group, the general similarity of these 
averages to those of the non-smokers together with the striking 
similarities of the curves in the two cases, make it quite probable 
that the habitual smokers as a group show a small loss in efficiency 
as the result of smoking. 

4. Habituation thus appears to have produced a partial toler- 
ance for tobacco in respect to memory span, reducing its effect 
perhaps something like a half. 

5. There is a marked tendency to remission on the second post- . 
dosage test with both groups of subjects. 

Two writers have published results showing the effect of 
smoking on memory span. Froeberg reports the averages from 5 
non-smokers on auditory memory span for consonants. He found 
an average loss in efficiency of about 14 per cent (Appendix G). 
Bush reports the results of two memory span tests on habitual 
smokers. One test was by visual presentation and the other was by 
auditory presentation. In marked contrast to Bush’s usually ex- 
aggerated effects, these results show losses of only 3 and 4 per cent 
respectively. 

Taking all of the available evidence into consideration, then it 
becomes quite clear that tobacco produces a detrimental effect 
upon memory span, at least for those not thoroughly accustomed 
to its use. Under the conditions of the present experiment, the loss 
in efficiency ranges around 5 or 6 per cent for non-smokers. The 
evidence is not quite so clear for habitual smokers. The general 
indications are, however, that they have a greater tolerance for the 
drug, showing an average effect, if any, not more than half as 
great as the non-smokers. 

In conclusion a word of caution may not be out of place in 


THE INFLUENCE OF TOBACCO SMOKING 131 


anticipation of a possible hasty and uncritical application of the 
above results to the ordinary learning process. The fact that the 
word “memory” appears in the name of the present test does not 
mean necessarily that we are dealing with the same process that 
goes by that name in the schools. There are points of resemblance, 
it is true, and these may be the ones upon which the detrimental 
effects just observed, depend. But the difference between the two 
processes are much more striking than the similarities. In our 
present ignorance we cannot say to which the effects are due. 
Meanwhile we must generalize with caution. 


CHAPTER XIV 


THE EFFECT OF SMOKING ON THE RATE OF LEARNING 


In the last chapter we considered the effect of smoking on the 
facility of the formation of the extremely short-lived associative 
bonds in auditory memory span. In the present one we shall con- 
sider the effect of smoking on the rapidity of the formation of the 
relatively permanent associative bonds in rote learning. The. 
material memorized consisted, in all, of 360 simple geometrical 
characters and as many nonsense syllables, one syllable being as- 
sociated with each character. On any given test, however, only 5 
characters with the corresponding syllables were used, because of 
the necessity for brevity in the test series.» About two-thirds of 
the 360 characters were taken from Moore.* The remainder were 
devised by the present writer. The 360 syllables used were chosen 
with great care from a list of 2200 specially prepared by the writer 
for the purpose. In choosing the 5 characters and syllables for any 
given test series, special care was taken to avoid, so far as possible, 
characters and syllables which should be confused with each other 
in the learning. To this end the vowel in the middle of each syllable 
was different in each of the five as was also the case with the initial 
consonant and the final consonant. A typical set of characters 
together with the corresponding syllables is shown in Plate 6. 

The mental processes of a subject while doing this test were 
somewhat like those involved in learning the vocabulary of a 
foreign language. The necessity for a rigid control of the various 
factors involved in the process required a rather elaborate tech- 
nique, though the task of the subject remained simple. The char- 
acters were presented to him one at a time, from the window of 
an automatic exposure apparatus of special design.* Exposures 
were of 5 seconds each and shifts from one exposure to the next 

1 See p. 35 above. 
2 Moore, T. V., The Process of Abstraction: An Experimental Study. Uni- 


versity of California Publications in Psychology, Vol. I, No. 22, 1910 
8 Hull, C. L,, op. cit., pp. 12 and 72. 


THE INFLUENCE OF TOBACCO SMOKING 133 


v4 
mise 
* 
J 


wv 
GUK 
Pate 6, A typical set of memory material. The syllables were presented to 
the subjects vocally. The diacritics indicate the pronunciation used. 


were practically instantaneous. Except at the moment of shifting, 
the character was stationary while being viewed. The window of 
the apparatus was I inch square and well illuminated, though in 
such a manner as to avoid a glare in the subject’s eyes. The syllables 
to be associated with the respective characters were taught to the 
subject by a prompting method. In the middle of each 5-second 
exposure, the experimenter spoke distinctly the syllable to be as- 
sociated with the particular character exposed, at the same time 
recording a minus sign in the appropriate part of the special 
scoring blank provided. The subject repeated the syllable and tried 
to associate it with the character. Upon the second appearance of 
a given character, if the subject could recall the associated syllable 
before the middle of the 5-second exposure (as indicated by the 
ticking of the clock work of the apparatus) a plus was recorded 
on the scoring blank and nothing was said. If he made an incorrect 
response or none at all, he was prompted as at first and given a 


134 GLARKR LD. HULL 


minus. The process was continued until the learning was complete. 
The score was the total number of promptings required. 

In order to insure that the associative bonds should be between 
the individual characters and the particular syllables assigned 
rather than a mere learning of the syllables in sequence as might 
easily happen by the usual method of memory experimentation, 
the 5 characters of a given series were presented to the subject 
always in 6 different chance orders. Not only this but the order of 
each of the 72 series of 5’s was different from the others. The 
presentation of each series in 6 different orders was made possible 
by the fact that over the drum of the apparatus could be placed a 
long canvas band which hung suspended from it and upon which 
could be placed a large number of characters. Thirty-six such 
bands were prepared, each bearing two complete sets of characters. 
Spurs on one edge of the drum engaged eyelets in the band to in- 
sure accurate movements. Moreover, 6 exact photographic dupli- 
cates of each character 5g inch square were provided. These were . 
attached to the band in the orders indicated, each by a drop of 
glue. Thus a total of 30 exposures were made before the original 
order was repeated.* By this time the learning was complete in 
nearly all cases. Accuracy in prompting was secured by a very 
careful system of key numbers on the scoring blank, corresponding 
to similar numbers on the band. 

The detailed scores showing the effect of smoking on the rate 
of learning of a typical subject, are shown in Table XXXVIII. 
These results, while somewhat erratic, show in general a loss in 
efficiency. The last period shows a satisfactory statistical reliability. 

The final results of the present investigation are shown in 
Table XXXIX and XL for the non-smokers and the habitual 
smokers respectively. An examination of the signs of the results 
on the first post-dosage test shows that the great majority of the 
subjects of both groups show a loss in efficiency as the result of 
smoking, 22 minutes after its termination. By the second post- 
dosage test, however, there has ceased to be any general agree- 
ment among the subjects. The final averages reflect the same situ- 


4 A second revolution was always made, however, to secure the data on speed 
of oral reaction to freshly learned material. : 


THE INFLUENCE OF TOBACCO SMOKING 135 


ation. The only final average which shows a satisfactory statistical 
reliability is that of the first post-dosage test of the non-smokers, 
though the average of the corresponding test with the habitual 
smokers has a statistical reliability of about 15 to 1. Both averages 
show a loss in efficiency of about 6 per cent. Because of the simi- 


TABLE XX XVIII 


Learning, subject No. 15, habitual smoker, Score, number of promptings re- 
quired to memorize five paired associates of nonsense material. 


Difference between normal of day 


Original scores and subsequent scores 
Test Test Test Test Test Test Test Average 

Control I Gh Bae Say II Ill IV Difference 
days: (Normal) 

Nov. 8 8 14 16 8 — 6 — 8 0 — 4.66 
oe 1'( 14 28 22 14 —14 — 8 0 — 7.33 
pomee LL 20 10 10 9 +10 +10 +11 +10.33 
als 8 im a 10 — 3 +1 — 2 — 1.33 
a6 11 14 11 9 — 3 0 + 2 — .33 
AS 19. HAs 9 10 2 ak aes + 1.66 
cam 19) 9 7 10 afl + 2 — 1 — 2 — .33 
ey: 18 12 18 ily + 6 0 +1 + 2.33 

Total TO Dell tet 0s 88 —10 — 2 +13 + .33 

Average 12.62 13.87 12.87 11 —125 — 2 +4162 + .04 

UNV Saree etccsts soa lateieless crests ravers ae 5.44 4.06 2.78 3.55 

Pat Meta cei aisaw ns «ass eu demes he 1.63 1.21 83 1.06 

Tobacco 
days: 

Nov. 7 28 8 22 24 +20 + 6 + 4 +10 
x 9 13 20 prea! 19 —7 + 2 — 6 — 3.66 
“2 yal 16 22 17 10 — 6 —i1 + 6 — .33 
Baie 7 9 10 13 — 2 — 3 — 6 — 3.66 
vente 8 180 8 10 — 9 0 — 2 — 3.66 
Pad Uf 10 17 14 11 —7 —4 —1 — 4.00 
se 20 10 12 14 20 — 2 — 4 —10 — 5.33 
a 21 13 9 10 14 + 4 + 3 —i1 + 2.00 
eB: 15 18 ap | 23 — 3 + 4 — 8 — 2.33 

Total 120 132 117 £144 —12 + 3 —24 —11.00 

Average 138.383 14.66 13 16 —138 + 33 —266 — 122 

IESE AME BEELER igo oie syeicinevs’s ¢.0:9.G.0:s 5.93 8.04 4.30 3.41 

3 LO ae) aa 1.67 86 1.21 96 

Effect of 

Tobacco: 

RP OEPUCEU Ree. oe ib. dis Youn Pur ase — 08 + 568 —428 — 1.26 

PIED aad ciel oils Vt 6 c's tia 0 868 2.33 1.48 1.46 1.43 

RCATIO NM Sorte cota ociaruete oe stolen eis 03 239 2.93 88 

PREM AD itvamerietss cictslncis sees ounce « 513 .606 976 -729 


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138 CLARK L. HULL 


larity of the conditions and results, probably both averages should 
be considered reliable. All evidence of evil effects have disappear- 
ed, however, by the second post-dosage test, 57 minutes after the 
termination of the smoking. 

The average number of promptings required to perfect the 
learning on the various tests throughout both the control and the 
tobacco days, was computed for both the non-smokers and the 
habitual smokers. These are shown by parallel curves in Figures 
16 and 17 respectively. It will be noted that the two sets of curves 


16 


ciates a 
b < 


°o 


@ 






S 


Number of promptings required to learn five paired asso 
» re.) 


°o 


1 2 3 4 
Number of test 





Tobacco days ===—~Control days 
Fic. 16. The effect of smoking on the rate of rote learning, non-smokers, 


THE INFLUENCE OF TOBACCO SMOKING 139 


16 









v =] ~ 
@ ro) i) rs 


Number of promptings required to learn five paired associates 
~ ‘ 


1 2 3 4 
Number of test 





Tobacco days -—-—-—Control days 


Fic. 17. The effect of smoking on the rate of rote learning, habitual smokers. 


show distinct similarities. Both originate at practically the same 
point. This argues well for the homogeneity of the test material 
as to difficulty.” Immediately after, there is a marked divergence 
of the curves, amounting to 9 or Io per cent of the average initial 
score in each case. This is followed immediately by an approach 
of the curves on the second post-dosage test, indicating a recovery 


5In this connection, it should be stated that the test material used on the to- 
bacco and the control days was varied with the different subjects, particularly 
with the smokers, with the purpose of eliminating any constant error which 
might chance to exist in the difficulty of the test material. 


140 CLARK LAHGLE 


from the effects, something less than an hour after the conclusion 
of the smoking. Both sets of subjects show an improvement in the 
rate of learning in the course of the experimental day, though the 
improvement of the habitual smokers is more marked than that of 
the non-smokers. As usual the group of non-smokers average more 
efficient than the habitual smokers. The difference has a reliability 
of only .935 so that it is not significant, probably being due merely 
to the chance sampling of the individual subjects. 

The result of the present investigation may now be briefly sum- 
marized : 

1. The non-smokers show a loss in the rate of learning im- 
mediately after smoking, of about 9 per cent. 

2. Recovery appears to be complete within an hour. 

3. The habitual smokers show an immediate loss in efficiency 
of about the same proportions, followed also by a recovery within 
an hour. 

4. Habituation in the matter of learning seems, therefore, to 
have no effect whatever. 

5. In the case of the habitual smokers, the tendency to remis- 
sion of the second post-dosage test noticed frequently in previous 
chapters, is quite marked. There is also a suggestion of this in the 
curves of the non-smokers. | 

Reports of the experimental investigation of the immediate 
effects of smoking on the rate of learning seems to be entirely 
lacking from the literature. This is especially to be regretted be- 
cause of the importance of the question involved, particularly as 
to its bearing on educational practice. Numerous statistical studies 
have been found, showing the relation between smoking and school 
marks, but these studies are quite inconclusive for reasons already 
given.® Our conclusion in this matter must therefore rest entirely 
on data given above. So far as this goes, the indication is that 
smoking produces a distinct immediate loss in the efficiency of 
rote learning, but that recovery is prompt. 


6 See p. 16 above. 


CHAPTER XV 
SUMMARY AND CONCLUSIONS 


The effects of smoking on the efficiency of the 12 forms of 
human behavior investigated in the present study have been sum- 
marized at the ends of the respective chapters. It remains to as- 
semble these results in a final survey of the investigation as a 
whole. The final numerical effects on the various functions are 
accordingly brought together in Table XLI. For purposes of sim- 
plicity and general intelligibility, percentage effects alone are given. 
Numerical reliabilities have been avoided by printing all effects 
having a satisfactory statistical reliability in special type, and by 
marking certain other effects which have been judged by the writer 
as probably reliable but partly upon other than statistical grounds, 
with a *,* 

In a similar manner the more important conclusions arrived at 
in the course of the various chapters may be summarized in a series 
of formal statements. These formulations apply primarily to the 
effects on the habitual smokers, for it is with the effects on these 
subjects that practical interest is mainly centered.? The list of 


1It should be noted that the percentage effects shown in this table have been 
computed in a different manner from those given in the summarizing tables of 
the various chapters. In the present case the percentages have been computed by 
dividing the average difference in score produced by the tobacco on the group 
as a whole, by the average score of the group on the first test of the experimen- 
tal day. As might be expected, the correspondence between the results by the 
two methods is very close in most cases. The present method has the advantage, 
however, of a closer functional relationship to the figure in each case upon which 
the chief statistical reliability is computed as well as to the data represented by 
the various curves throughout the preceding chapters. If desired, the interested 
reader may easily compile for himself a table of the other type of percentages 
from the final averages of Tables V to XL, as well as one showing the reliabili- 
ties, the absolute differences, etc. 

2It is true that from the point of view of pure science the effects on non- 
smokers are as important as those on habitual smokers. Results with non- 
smokers also serve an extremely important practical purpose by aiding in the 
interpretation of the results of the smokers. It is merely implied by the above 
statement that the effect of tobacco on people who don’t use it is not in itself a 
practical problem. 


CLARK L. HULL 


142 





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THE INFLUENCE OF TOBACCO SMOKING 143 


formulations also includes near its end a number of more general 
conclusions here stated for the first time. 

I. There is a marked and uniform stimulation of the heart 
rate, a considerable amount of which is still present an hour and 
40 minutes after smoking. 

2. There is evidence of the greater susceptibility of the heart 
to the influence of excitement after smoking. 

3. There is a large and uniform increase in the tremor of the 
hand. The most of this has disappeared an hour and 23 minutes 
after smoking. 

4. There is probably no uniform effect on the rate of tapping. 
If such exists it is too slight to be measured by the present meth- 
ods and number of subjects. 

5. The effect on the ability to resist the onset of muscular fa- 
tigtue is uncertain, though there is a little indication that resistance, 
at least to a certain type of fatigue, may be increased. 

6. There is probably no measurable effect whatever on can- 
cellation. If any exists it is in the direction of a very slight (ab- 
solute) gain in accuracy at the expense of an equally slight loss 
in speed. 

7. There is a fair probability of a minute increase in the speed 
of reading reaction-time, both to old and to recently learned 
material. 

8. There is a marked and uniform gain in the rate of com- 
plex mental addition. This stimulation has not begun to decline 
an hour and 15 minutes after smoking. 

g. There is no measurable effect on the accuracy of complex 
mental addition. 

10. There is high probability of a loss in auditory memory 
span. 

11. There is probably a loss in the efficiency of rote learning 
immediately after smoking, though it is apparently followed by a 
recovery within an hour. 

12. There is no uniformity in the time required for the max- 
imum effects of tobacco to appear with the various tests. The most 
general statement that can be made on the basis of the present 
data is that in the case of unfavorable effects the maximum tends 


144 CLARK L. HULL 


to appear immediately after smoking but favorable effects tend to 
appear most strongly at the close of the experimental period, 
roughly 114 hours after smoking. 

13. The influence of habituation on the effects of smoking is, 
in general, favorable where it has any influence at all. It is note- 
worthy, however, that with the majority of the processes that 
show tobacco effects (heart rate, tremor, reading reaction-time, 
learning reaction-time, rote learning) there is no indication what- 
ever of a tendency for habituation to produce a tolerance.*® Certain 
processes (resistance to fatigue, accuracy in addition, memory 
span) do show a diminution in effect as the result of habituation. 
In two cases (accuracy in the A-test, complex mental addition) 
habituation has apparently produced a complete reversal effect. 

14. There are numerous indications of a tendency to tempor- 
ary remission of the ordinary tobacco effects in the period around 
50 minutes after smoking, followed by a recurrence of the original 
effect some 35 minutes later. Superficially this appears to be a kind 
of rhythm in the action of the drug which, so far as the present 
writer has been able to discover, is unique in pharmacology. This 
may be the case. It seems more likely, however, that this tendency 
to a recurrence of the original effect at the close of the experimen- 
tal period may be due to a mild excitement on the part of the 
subjects at nearing the end of the day’s work.* Owing to the nature 
of the control methods used in the present experiment, this neces- 
sarily requires that the subjects should be more susceptible to this 
excitement on the tobacco days than on the control days. We have 
already seen evidence (p. 55) that an effect of exactly this nature 
exists in the case of heart rate. Moreover, with heart rate it is 
well known that the effects of the drug and of excitement are 
identical, which is distinctly suggestive. In the case of the four 
mental processes showing the tendency to recurrence of the to- 
bacco effect (reading reaction-time, learning reaction-time, audi- 
tory memory span, rote learning) the identity of the influence of 


8 This is in marked contract to the rather prompt establishment of a fairly 
complete tolerance with respect to the well known vomiting reactions common 
with beginning smokers. 

4 Rivers, op. cit. See p. 24 above. 


THE INFLUENCE OF TOBACCO SMOKING 145 


the two factors of drug action and excitement, while probable, is 
by no means as certain as with heart rate. In any case the principle 
of explanation is an interesting one and, if true, may throw light 
on the nature of the action of tobacco on the higher mental pro- 
cesses. Its obvious relation to the emotions also suggests the pos- 
sibility of a clue to the charm which tobacco has for those ac- 
customed to its use. Moreover, the well known relation of the 
emotions to the endocrine glands raises the possibility of a specific 
action of tobacco upon the latter. But at present the explanation 
put forward above must be regarded merely as an hypothesis. As 
such it may be formulated as follows: Excitement tends in certain 
mental processes to reinstate tobacco effects where recovery is in 
progress or has recently taken place. 

In a final review of the various effects of. tobacco enumerated 
above, it will be noted that only three of the 12 forms of behavior 
investigated reveal an unmistakable influence of smoking. Two of 
these (pulse, tremor) are essentially physiological. The interest 
of the present investigation, on the other hand, is primarily in the 
more strictly psychological processes. Of these, only one (addi- 
tion) shows an unmistakable effect. Several others show effects 
with a fair degree of reliability, however, and are entitled to con- 
sideration. Probably the two most significant tests of this intel- 
lectual group as revealing the influence of smoking on mental 
efficiency, are complex mental addition and rote learning. The first, 
together with reaction-time may be presumed to give some indica- 
tion of the effects of smoking upon ordinary routine thinking, 
which is essentially the functioning of old associative bonds. The 
evidence in this case is favorable to tobacco where the subject is 
an adult and is accustomed to its use. Rote learning, on the other 
hand, possibly supported by memory span, presumably indicates 
the effect that tobacco is likely to have where new associative 
bonds are in the process of formation, as in most school learning. 
The results in this case, while not so reliable, are unfavorable to 
tobacco. It must be remembered, of course, that the above formu- 
lations apply with strictness only to the first hour and a half after 
the termination of the smoking. Generalizations from them must 
be made with extreme caution. 


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APPENDIX B 


G. A. Dow.ina’s RESULTS ON HEART RATE 


The results of G. A. Dowling’s experiment have briefly been 
reviewed in Chapter I. Dowling had subjects do strenous jumping 
after smoking and then counted the pulse the first 15 seconds of 
each of the first 15 minutes following. A control series was run in 
which the subject jumped but did not smoke. Fisher and Berry 
draw certain conclusions from Dowling’s results which would be 
extremely important if true, but which, upon careful examination, 
seem quite without logical foundation. The present writer has 
taken the trouble to compute from Dowling’s published scores, the 
average rate for the various smoker subjects for the first, fifth, 
tenth, and fifteenth minutes after jumping. Where Dowling ceased 
counting before the end of the 15 minutes, it has been assumed 
that the pulse continued at the rate given in his last recorded count. 
The averages in the following table have been computed on this 
basis rather than (as Dowling did with the non-smokers) on the 
basis of the few cases which happen to be above normal and so got 
recorded. 

It will be seen from the table that the pulse stimulation per 
minute on the first, fifth, tenth and fifteenth minutes after smoking 
is 6.0, 8.8, 6.4, and 6.0 beats respectively. Fisher and Berry con- 


SMOKE DAYS CONTROL DAYS 
No. Heart Beats per 15 sec. No. Heart Beats per 15 sec. 
Subject |Normal| after smoking and jumping iia after jumping alone 
pa ete 5th flor | i5th cart 7st | Sth | 10th | 16th 
ate : : . : Rate . ‘ 
min min min min min min min, min 


oe ge) ee SS Sra Se eee S| ores | ee eee ene eee 


x 

ig 

Zz 

M 

N 

ai 

W 86.6 35.3 22.4 22.5 22.5 85.8 34.8 21.4 21.2 21.2 
Average 
Per min 


148 CLARK L. HULL 


clude from Dowling’s results that smoking delays the recovery 
of the heart from a stimulation which is the result of exercise. As a 
matter of fact all the results prove is that the ordinary stimula- 
tion due to smoking persists relatively undisturbed by the jump- 
ing, for at least 15 minutes. Surely, the jumping had nothing to _ 
do with this, for our own results have shown that the pulse has 
by no means returned to normal after nearly 2 hours where there 
was no jumping whatever. The experiment should have been set 
up quite differently to make a solution of Dowling’s problem pos- 
sible. | 

Fisher and Berry also conclude from Dowling’s results that 
smokers have a normal heart rate higher than non-smokers. The 
present writer has averaged the pre-dosage rate for both the con- 
trol and the tobacco days for each subject of the two groups. They 
appear in the following table: 


SMOKERS NON-SMOKERS 

83.9 Difference 2.4 
79.5 82.3 
75.5 82.3 PED 2.19 
74.0 80.5 
77.0 88.9 Ratio 1.09 
88.3 68.1 
87.5 TT Reliability 
86.2 73.8 of .770 
—_— od difference 

Average 81.5 [9.1 

P. E.m 1.49 1.61 


It will be seen that the averages show a slightly higher rate for the 
smokers, but a computation of the statistical reliability of this 
difference shows that a difference as large as this would under the 
present circumstances happen by pure chance in about 2 cases in 
10. Such a statistical reliability is of course far below the lowest 
limit ever accepted in scientific work. Fisher and Berry’s gener- 
alization is therefore quite unwarranted. 


APPENDIX C 
WarrEN P. LomBArp’s RESULTS ON MUSCULAR FATIGUE 


The results of Lombard’s investigation of the effects of tobacco 
on muscular fatigue have been reviewed in Chapter I. His publish- 
ed results are summarized in the following table: 





CONTROL DAYS TOBACCO DAYS 
Amt. of work Amt. of work 
Date in Kgrm. Date in Kgrm. 
March 6 11.25 March 2 15.00 
ss 7 15.15 Me 3 11.31 
¥ 8 18.69 = 4 8.79 
S12 19.02 ¥ 5 8.04 
: 9 18.71 
om: 10 12.48 
ihe 10.29 
Average 16.027 11.374 
Pb 1.193 645 
Difference 4.653 Kgrm. in favor of the control days 
P. E.p 1.356 
Ratio 3.43 


Reliability .989 


APPENDIX D 
VAUGHAN HAarLEyY’s RESULTS ON MUSCULAR FATIGUE 


The result of Harley’s investigation of the effects of smoking 
on muscular fatigue have been reviewed in Chapter I. His publish- 
ed results are summarized in the following table. This shows the 
average gain or loss as the result of smoking from six experiments. 
A plus in Harley’s published results means that the control per- 
formance was more efficient than the drug performance. 


No. seconds gained or lost 
in resisting fatigue as result 
of smoking 


No. Kgrm. gained or lost 
as result of smoking 


+1.876 73 
ES KEG —27 
+1.010 +26 
+1.795 —40 
SETH Es 
— .450 —10 

Average = + .558 + 4.80 

P. Ew sx 380 10.40 

Ratio a 1.470 46 

Reliability = 836 62 


APPENDIX E 
THEODORE HouGu’s RESuLTs ON MUSCULAR FATIGUE 


The results of Hough’s investigation of the effects of tobacco 
on muscular fatigue have been reviewed in Chapter I. His rather 
meagre published results are summarized in the following table: 


CONTROL DAYS TOBACCO DAYS 
Diff. between before ‘ 
y Diff. between before 
Date and ode Se Date and after smoking 
May 8 + 70 May 7 + 90 
in 9 +110 cae aL +240 
oe —140 
elo — 30 
Average + 2.50 +165 
PIE hk 37.00 44.8 
Net difference = 163.5 sec. in favor of the tobacco days 
P. En ea 53.1 
Ratio = 2.81 
Reliability = 971 


APPENDIX F 
C. S. Berry’s RESULTS IN ADDING 


Charles Scott Berry’s results regarding the effect of smoking on 
adding have been reviewed above, Chapter I. The significant part 
of his published table of results is reproduced below. Since his 
tobacco days are in all cases one day later than his control days 
and hence have the advantage of one day’s practice effects, the 
difference which he finds between the averages of the two sets of 
days in reality are a compound of tobacco effects and practice 
effects. In order to eliminate these practice effects, the present 
writer has computed for each tobacco day the amount of gain in 
speed over the average speed of the day immediately preceding it 
and the day immediately following it. This has been done on the 
assumption that the average of these two days will give, on the 
long run, the approximate non-drug speed of the tobacco days 
had tobacco not been used. This difference, then, should give us 
the approximate tobacco effect undisturbed by practice. Since there 
is no control day following the last tobacco day, the last entry of 
our column of effects was obtained by finding the difference be- 
tween the last control day and the average of the tobacco days 
immediately preceding and following it. 

Berry’s computations show a gain of .5 of a point in accuracy 
and of go seconds in speed. These are gains of 4.5 per cent and 7.7 
per cent respectively over the non-smoking days. When practice 
effects are eliminated as indicated above, the .5 gain in accuracy 
becomes practically zero and the 90 seconds gain in speed to 70.7 
seconds or 6.1 per cent. The statistical reliability of the effect on 
speed is extremely satisfactory. 





SUMMARY OF FROEBERG’S RESULTS? 


APPENDIX G 


This table reproduces Froeberg’s tabular summary of his second experiment. In addition the reliabilities of the results of the individual subjects, the percentage effects and the 
statistical reliabilities of the group averages have been supplied by the present writer. Plus means a gain in efficiency as result of smoking, minus means a loss. 








MEMORY 
Subject Gain |Prob-| Reli- |] Percent 
or able | abil- gain 
loss error| ity or loss 
Bu —14.00 | 6.10 | .939)| —23.40 
H —14.00 | 6.30} .931])} —20.00 
i= —24.00 | 3.80 |1.000}} —37.00 
R —13.20 | 5.10] .960)| —25.50 
W +16.80 | 6.40 | .960)) +38.10 
Average — 9.68 | 5.54 —13.56 
M. V. 10.59 20.66 
P. Ew“ 44.00 7.81 
Reliability (A) 950 88 
Par 2.48 
PB tet hits ‘eB) .996 








FREE ASSOCIATION 








Gain |Prob-| Reli- || Per cent 
or able | abil- gain 
loss error | ity | or loss 
—6.30 | 2.00 | .983 || —15.60 
—3.00 | 1.10] .966 || — 9.40 
—7.80 | 2.80 | .970 || —17.40 
—3.50 | 1.80 | .905 |} —15.20 
—1.80 .80 | .935 || — 7.80 
—4.48 | 1.70 | —13.08 

2.06 3.58 
.78 1.35 
1.00 1.00 

| 
.76 
1.00 


Gain 
or 
loss 


—2.60 
+1.80 
—4.20 
—1.80 
—6.10 














ADDITION 
Prob-| Reli- |} Per cent 
able | abil- gain 
error | ity or loss 
4.40 | .857 || — 4.10 
1.00 | .889 || + 3.60 
2.30 | .890 || — 7.70 
2.20 | .705 || — 4.00 
3.80 | .859 || —17.40 
2.74 | — 5.92 
5.30 
2.00 
| 9 





OPPOSITES 
Gain |Prob-| Reli- || Per cent 
or able | abil- gain 
loss error | ity | or loss 
+ .60 .60 | -750 || + 3.40 
-—1.90 .40 | .999 —11.30 
—1.20 | 1.20] .750 || — 6.00 
— .30 .80 | .593 || — 2.20 
— .60 40 | .844 || — 5.00 
— .68 .68 — 422 
.69 3.85 
.26 1.46 
-960 .974 
30 
.934 





COMPLETION 
Gain |Prob-| Reli- || Percent 
or able | abil- gain 
loss error | ity or loss 

1.51 | 2.54 | .657 — 

Ey Ae SEMEL ae —_ 
SlanlLsoonl OSU 
Ae |peayew ly Sisats? — 
2.29 | 1.74] .809 _ 
1.04 | 2.02 
.68 
.26 
996 
90 
-781 





1Journal of Experimental Psychology, Vol. 3, p. 334 ff. 


THE INFLUENCE OF TOBACCO SMOKING 153 








Tobacco effects after 


Reproduction of Berry’s Table Pircotiosiston practice 


Errors Time in min. and sec. 


Day FoR ae ETDS Bee | ea ee RT a eR Errors | Time in sec. 
Smoking |No smoking|} Smoking {No smoking 


22 _ 23 :50 — —_— 


1 ee 
2 12 +3 21:30 DS +45 173.5 
3 — 11 = 21:37 ar = 
4 10 a 19 :38 = See Hee-b8. Oe 
5 , 8 eae 19:55 = aE 
6 18 = 18:45 = —3.5 150.0 
7 aa 21 =o 19:15 ee oe 
8 15 7m 18 :10 = 0 +66.0 
9 on 9 aa 19:17 a os 
10 5 << 18:3 an +3.0 +54.0 
‘di xt 7 aes 18:37 aoe a 
12 10 ex 17 :23 at —2.5 +70.7 
13 =e 8 14. 18 :30 pat ase 
14 8 cas 16 :23 oe —0.5 198.5 
15 te 7 ie 17:33 Le a 
16 14 = 15 :50 <= —5.0 189.5 
17 an 11 oi 17:6 0m ae 
18 6 a 16 :27 as +4.0 +56.0 
19 we 9 = 17 :40 E70 +81.0 
20 10. RE 16:11 ie = pee 
Average 10.8 11.3 17:50 19 :20 + .05 +70.7 
P. E.m 3.20 
Ratio 22.10 


Reliability 1.00 





APPENDIX H 
BAUMBERGER AND MarTIN’sS RESULTS 


The investigation of Baumberger and Martin as to the effect 
of smoking on the efficiency of telegraph operators has been re- 
viewed in Chapter I. These writers make a commendable effort at 
a statistical evaluation of their results. Unfortunately they used 
an erroneous method of computation with the result that their 
final conclusions are largely unwarranted by their facts. They 
state quite truly “that differences between means to be significant 
must contain the probable error twice and should contain it three 
times. . . .”” They made the mistake, however, of taking as the 
probable error of the difference (P. E.p) the average of the prob- 
able errors of the two means from which the difference was ob- 
tained. As a matter of fact the probable error of the difference 
between two means, is the square root of the sum of the squares 
of the probable errors of the two means. 

The formula is:* 


LEA Wy stor Meee deh + P. E? 
D M, M, 


Naturally the probable error of a difference is a much larger figure 
than the average of the probable errors of the two means. It is 
because of this that Baumberger and Martin in a number of cases 
report as reliable drug effects, what in reality may be nothing more 
than the result of chance errors of sampling. The following table is 
largely a reproduction of a table published by Baumberger and 
Martin showing their results and method of computation. The 
present writer has made the appropriate computations from Baum- 
berger and Martin’s figures by the approved formula and the re- 
sults are given in adjoining columns. It will be seen at a glance that 
the computed ratios are much smaller than those given by Baum- 
berger and Martin, and only two of the nine attain a satisfactory 
degree of reliability. 

They do not state how they computed the probable errors of 


1 Thorndike, E. I., Mental and Social Measurements, p. 193. Whipple, G. M., 
Mental and Physical Tests, p. 27. 














THE INFLUENCE OF TOBACCO SMOKING 155 
BAUMBERGER AND MARTIN’S TABLE peat rey 
Ratio of 
Rate for Rate for Ratio of difference 
Hour Heavy Smokers Light Smokers Difference to the 
of Difference |to Average|| P. E.p Probable 
day iin ca (eas ee | OO RR kc Probable Error 
Mean P. Ew Mean 1 Ti Error of the 
Difference 
i 37.80 +0.91 28.48 162 —9.32 —7.3 1.86 5.00 
2 45.02 +1.66 48.21 +£2.36 +3.19 1:5 2.89 1.10 
3 42.25 +#1.25 43.30 +2.02 +1.05 0.6 2.37 44 
4 38.77 +1.14 43.00 aural sf ( 4.33 3.1 1.94 2.23 
5 38.98 sag) Fw 8 44.75 +2.12 +5.75 oto 2.41 2.39 
6 31.64 +1.08 40.00 +2.20 +8.36 5.0 2.45 3.41 
af 39.10 1.50 33.92 +£2.30 —5.18 —2.7 2.75 1.88 
8 38.50 t=1295 41.50 2.50 +3.00 1.3 Shi hy .94 
9 29.80 +1.60 37.50 +2.74 Sete 3.5 3.18 2.42 
Average 38.00 1.358 40.07 2.159 2.09 


their means. There are some indications that this may also have 
been done by an incorrect method. The present writer has com- 
puted the entire set from the standard deviations which are pub- 
lished. In almost every case the computation yields much larger 
probable errors than Baumberger and Martin give. Those from 
heavy smokers average 1.80 and those from the light smokers 
average 2.66. When the P. E.p’s are computed from these probable 
errors, the rations become still less than those shown in the last 
column of the above table. For example, the one for the sixth 
hour which by the above table is still above 3, shrinks to 2.64. 

It is impossible to determine in a wholly satisfactory manner 
from their published data the reliability of the final average differ- 
ence between the light and heavy smokers for the day as a whole. 
A fair approximation to it may be obtained by taking the average 
probable error of the hourly means as the probable error of the 
average hourly rate for the respective groups. This method yields 
a probable error of the difference between the day’s output of the 
two groups, of 2.55, whereas the difference itself is only 2.09. This 
gives a ratio of .81 which corresponds to a reliability of .710 
which is quite negligible. Their results are accordingly quite in- 
decisive as to the relative total daily output of light and heavy 
smokers. 


APPENDIX I 


MEYLAN’S RESULTS ON SMOKING AND SCHOLARSHIP 


The investigation by George W. Meylan of the effect of smok- 
ing upon university grades has briefly been reviewed in Chapter I. 
Meylan concluded that the relation between smoking and scholar- 
ship was so complicated by other factors that it was impossible 
to tell whether tobacco had any real causal effect or not. As a 
matter of fact the situation, while complex, yields quite readily 
to mathematical analysis. The present writer has taken the trouble 
to make the necessary computations from Meylan’s published re- 
sults and the various operations and results are indicated below. 
Unfortunately Meylan’s tables do not always supply the necessary 
information in exactly the form that is desired, which has necessi- 
tated a certain amount of interpolation. For this reason as well as 
by reason of the small number of data, the result of this computa- 
tion are not to be regarded as having any considerable reliability. 
They are given rather as an illustration of a method which may 
be employed in the investigation of this extremely important prob- 
lem. The data upon which the following computations are based, 
appear in the following table.* 

Since the analysis is to be accomplished by means of partial cor- 
relation, it is first necessary to secure all the correlations of zero 
order among the four variables. The ordinary product-moments 
method can not be used here because of the all-or-none nature of 
many of the variables. The coefficients may be computed quite 


1 The figures in the two columns under “scholarship” were in all cases de- 
rived from Meylan’s published tables showing the average of the marks of the 
various groups. It was assumed in these computations that I point in school 
marks corresponds approximately to .12 of the standard deviation of the distri-— 
bution of the grades in any given group (D. Starch, Educational Psychology, 
p. 442), Assuming a normal distribution it is easy by means of a probability 
frequency table to tell approximately the number of men of one group falling 
above or below the median of another group, once the difference in average 
mark is known. 


SMOKING 


FRATER- 
NITIES 


ATHLETICS 


THE INFLUENCE OF TOBACCO SMOKING 


Number of 
Smokers 


Number of 
Non-Smokers 


Number of 
Fraternity 
Men 


Number of 
Non- 
Fraternity 
Men 


Number of 
Men who 
Made 
Athletic 
Teams 


Number of 
Men who 
did not make 
Athletic 
Teams 


115 





139 


SCHOLARSHIP SMOKING 
Number Number 
of men of men 
falling above 
below the Number a bed 
the average of N 
average of Smokers s a 
of the the as 
better better 
group group 
92 23 
54 54 
58 8 49 17 
79 78 66 91 
61 23 47 37 
70 69 68 ffi 





157 
FRATERNITIES 
Meaber Number 

of 

of 

Fraternity age 
Fraternity 
men 

men 
41 43 
25 114 





readily, however, by means of the four-fold table method. The 
formula used in the present computation was :? 


Vbec 
r == cos —— ee 
t Vbe + Vad 


If sufficient data were available to yield really reliable results, 
Pearson’s more accurate method should, of course, be used. With 


2 Whipple, G. M., Mental and Physical Tests, Simpler Processes, p. 48. 





180° 





158 CLAREAL. HULL 


the aid of special tables now available® the labor of computation 
by Pearson’s method is no longer excessive. 

The various correlations of zero order resulting from these 
computations appears in the following table: 


Poor 


Scholarship Smoking Fraternities 
1. Poor Scholarship 
2. Smoking +.50 
3. Fraternities +.66 +.50 
4. Athletics +.36 + .11 +.53 


It is next necessary to determine what the correlation between 
smoking and poor scholarship alone would be, if the influence of 
fraternities and athletics on scholarship were eliminated. This is 
accomplished by means of partial correlation. The formula is :* 


r Kosa "13 a "23 


12.30 = —§-_ —__—_ 
I—r I — 1 
V ey ip 
The final result is accomplished by a series of applications of the 
formula resulting in successive eliminations. The results obtained 
at the various stages of the process are as follows: 


Correlation, poor scholarship and smoking, athlectics constant...... «<0 aoe 
Correlation, poor scholarship and fraternities, athletics constant....... +.59 
Correlation, smoking and fraternities, athletics constant ...........ee- “1-52 
Correlation, poor scholarship and smoking, both athletics and fraterni- 

ties" Constant’ so ose kell e sates cece Cae ete a ee = wats bat TEE 


The last entry in the above series gives us what we are seeking. 
It shows that the correlation between poor scholarship and smo- 
king is reduced from +-.50 to +.27 or approximately half, when 
the influence of athletics and fraternities are eliminated. 

It is also a matter of some interest to know what the difference 
between the averages of the marks of the two groups would be 


3 Pearson, Carl, Tables for Statisticians and Biometricians, p. 42 ff. 
4 Yule, G. U., Introduction to the Theory of Statistics, p. 239. 


THE INFLUENCE OF TOBACCO SMOKING 159 


with the influence of athletics and fraternities removed. By substi- 
tuting appropriately in the above correlation formula it is found 
that under the new conditions 77 of the smokers would fall below 
’ the median non-smoker or 15.8 per cent more than would if the 
two groups were of equal scholarship. This amounts to .41 of the 
standard deviation of the grades of the groups. Assuming .12 of 
the standard deviation to correspond to I point in school marks, 
this deviation would correspond to a difference between the two 
groups in average standing, of 3.4 points. 


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3sa}-Y ‘Aoeinsoy 
3S9}-y uo paads 
ansiyey Iepjnosn yp 
Suidde} jo o}eyY 

puey jo sows1 7 


9381 JIeOLT 


daLsaL SNOILONNA 








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ayy 40f a4ay uanmb asp Kay] *4404a4 posauab ay} ut papnjaut u2aq 40Uu asofasayy aavy Kay] ‘ajqpyas pasapisuo? 1OUu 24am StINSa4 
S14 PUD 104JUOI aYt PasaQoISip jIalqns Sty] “4ayoUS JONJIQDY UD ‘FI ‘ON 4IaLqQus fo SynSa4 ay} SaztaDMuns ajqv} Buumojof 24 1 


{ XIGNAddV 


APPENDIX K 


ARYFRNJLVAABAHPYKKQAKPALEWNAIPAAEHANAO 
AZQUWBIJXAGLONDSEMRAJYQAFAVUYADOAYADCWA 
AFRAAKUATAAAWCFZAAUDFEHMSLBAXBACZJOVAW 
IUMUYZXAJFDGKTOFFSAOCLAMVYVASDZAJAIATBAC 
AGYHUZSHRGOJTNAPJRWOPODCMAUEEIMNXDGTAQ 
AMUIXATOPOGCTNVAGXKAARCADAHDOBAFXLDWYI 
RWXBGXBIUQADSJNMPAGAVAWIYZMXMNZTEAAAZA 
MAHHMGKPIAAWCGNSWALTORYAKCGDXKSTAVUXX 
KLPVAOYAASOLRVXISOADSYTVILPAOVJUAENNJLKP 
SPOULVRBJQUANAAJHFBIQGHVAVENAICIPRENTELA 
AAWBGNWSORXOXGOCHPSQUQWBLARRAZAZIEMDT 
APKNKBCAJZPBSLRJHHEASFFTNAVBWZAEAAALEWA 
HCRVASTYWALAUVGFKEADHOFABQKCTAFAYNCWHA 





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BF21 .P96 v.33 
The effect of manual guidance upon maze 


ini 


Theo 


| 


iii 


1 1012 00008 5433 





